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An 85-year-old man presented for an itchy rash of his right lower leg for approximately 12 weeks. For the past 3 weeks, he had been applying triamcinolone 0.1% cream to the area twice daily without improvement. Cutaneous examination of the right distal leg revealed an annular red plaque with a raised purpuric border, measuring 13×10 cm (Figure). A biopsy was performed for further evaluation.
What is Your Diagnosis?
To find out the answer and case details, go to page 2
Diagnosis: Tinea Incognito
Tinea incognito is a dermatophyte infection of the superficial skin whose morphology differs from the typical tinea corporis due to topical application of an immunosuppressive medication—most commonly a corticosteroid.1
Dermatophytes derive sustenance by metabolizing keratin and infect their hosts by invading keratinized structures such as hair, nails, and the stratum corneum of the skin.2,3 Tinea corporis is transmitted between hosts by skin-to-skin contact, or through fomites.1 Dermatophyte infections are common and between 20% and 25% of the world population is thought to be affected.4 The most common culprit dermatophyte of tinea incognito is Trichophyton rubrum.1
Clinical Presentation
Tinea corporis typically presents on the trunk or extremities as erythematous, annular, papulosquamous lesions with a fine scale, raised borders, and central sparing.1 Application of immunosuppressive medications such as topical corticosteroids, topical pimecrolimus, or topical tacrolimus can significantly alter the clinical appearance of tinea corporis.1 This presentation is termed tinea incognito, and represents approximately 40% of tinea infections.1 Tinea incognito will appear less inflammatory with less scaling than traditional tinea corporis.2 The margin is typically less raised and the lesions may be more pustular and extensive5 (Figures 1A and B).
Pathogenesis
The presence of dermatophytes such as T. rubrum in the stratum corneum elicits an eczematous inflammatory response in the skin layers below.3 Eczematous skin produces keratin less effectively than healthy skin, thereby starving the dermatophyte of sustenance.3 Topical immunosuppressive medications such as corticosteroids, dampen this eczematous response, and in effect, create a more hospitable environment for the dermatophyte to grow.3 Tinea incognito is most likely to occur with application of strong immunosuppressive medications such as fluorinated corticosteroids.2,3 The risk is also increased when these medications are applied under occlusion.2 However, the presentation of tinea corporis can be altered even with application of low-potency steroids such as 1% hydrocortisone cream.2
Pathology
The first step in diagnosing a superficial fungal infection is preparing a potassium hydroxide (KOH) slide preparation for microscopic examination with superficial skin scrapings from the area of concern.6 The presence of hyphae on KOH testing confirms the diagnosis of a dermatophyte infection.6 For typical tinea corporis infections, skin biopsy is rarely indicated.6 However, for patients in whom a superficial fungal skin infection is not suspected or in whom tinea incognito is suspected but not confirmed with examination of a KOH preparation, ruling out other disease processes through biopsy is an appropriate diagnostic approach. Additionally, if Majocchi granuloma (a deep and persistent fungal infection of the hair follicles) is considered in the clinical differential diagnosis, a biopsy may be necessary to identify hyphae within the portion of the hair follicle that would not usually be detected on a superficial skin scraping for a KOH preparation.
The hyaline fungi can be difficult to identify on hematoxylin-eosin (H&E) staining. However, an astute pathologist can sometimes identify the organisms presenting either in cross section or longitudinally between keratinocytes in the stratum corneum. In contrast, using either periodic acid–Schiff (PAS) or Gomori methenamine silver (GMS) stain enables the fungal hyphae to easily be recognized.4
Microscopic examination of the H&E-stained sections reveals mild hyperkeratosis with focal parakeratosis, spongiosis, and neutrophilic microabscesses.4 Perivascular lymphocytes, mild edema, or both may also be present in the dermis (Figures 2A and B).4 Microscopic examination of PAS-stained sections readily demonstrates fungal hyphae in the stratum corneum (Figures 3A and B).
Differential Diagnosis
Tinea incognito represents a diagnostic challenge for clinicians because it commonly mimics other skin disorders. Tinea incognito is most commonly misdiagnosed as eczema, impetigo, lupus erythematosus, rosacea, and psoriasis.1 Other possible diagnoses that could be included in the clinician’s differential include erythema annulare centrifugum, erythema migrans, granuloma annulare, pemphigus foliaceus, and pityriasis rosea.5,7 The skin lesions of tinea incognito can also mimic contact dermatitis, lichen planus, purpura, and seborrheic dermatitis.5
Management
Localized tinea corporis can generally be cured with topical antifungal medications. However, oral antifungals may be necessary for tinea incognito, particularly if they do not resolve with topical therapy.2 Itraconazole, fluconazole, or terbinafine are the first-line agents used to treat tinea incognito.2 These medications tend to concentrate in the keratinized stratum corneum where the dermatophyte resides.2 For tinea incognito, neither a recommended duration of treatment, nor a specific systemic agent has been established.2
Our Patient
The possibility of Majocchi granuloma was entertained; therefore, a lesional skin biopsy from the border of the lesion was performed. Microscopic examination of the H&E-stained sections showed orthokeratosis, and mild acanthosis in the epidermis and a sparse perivascular lymphocytic infiltrate in the dermis (Figures 2A and B). The PAS-stained sections highlighted florid hyphae scattered throughout the stratum corneum (Figures 3A and B). The clinical presentation, history of topical corticosteroid use, and pathology findings confirmed a diagnosis of tinea incognito.
Topical treatment with ketoconazole 2% cream twice daily was initiated. Evaluation after 4 weeks of treatment showed that the lesion had completely resolved.
Conclusion
The incidence of tinea incognito is increasing due to readily available over-the-counter topical corticosteroids, the misuse of strong topical corticosteroids, and self-treating patients with excess corticosteroid ointments from previous dermatoses.3,7 Clinicians should include tinea incognito on their differential diagnosis when a patient presents with annular plaques that are unresponsive to topical corticosteroids. If suspected clinically, a biopsy should be performed with PAS or GMS staining to confirm the diagnosis. In our patient, a definitive diagnosis was made and appropriate treatment was started.
Dr Cox completed medical school at Louisiana State University Health Sciences Center in New Orleans, LA. She looks forward to beginning her intern year at Scripps Mercy Hospital in San Diego, CA.
Dr Cohen is with the department of dermatology at the University of California, San Diego in San Diego, CA.
Disclosure: The authors report not relevant financial relationships.
References
1. Segal D, Wells MM, Rahalkar A, Joseph M, Mrkobrada M. A case of tinea incognito. Dermatol Online J. 2013;19(5):18175.
2. Jacobs JA, Kolbach DN, Vermeulen AH, Smeets MH, Neuman HA. Tinea incognito due to Trichophytom rubrum after local steroid therapy. Clin Infect Dis. 2001;33(12):E142-144.
3. Ive FA, Marks R. Tinea incognito. Br Med J. 1968;3(5611):149-152.
4. Guarner J, Brandt ME. Histopathologic diagnosis of fungal infections in the 21st century. Clin Microbiol Rev. 2011;24(2):247-280.
5. Guenova E, Hoetzenecker W, Schaller M, Röcken M, Fierlbeck G. Tinea incognito hidden under apparently treatment-resistant pemphigus foliaceus. Acta Derm Venereol. 2008;8(3):276-277.
6. Sahoo AK, Mahajan R. Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review. Indian Dermatol Online J. 2016;7(2):77-86.
7. Kim WJ, Kim TW, Mun JH, et al. Tinea incognito in Korea and its risk factors: nine-year multicenter survey. J Korean Med Sci. 2013;28(1):145-151.
An 85-year-old man presented for an itchy rash of his right lower leg for approximately 12 weeks. For the past 3 weeks, he had been applying triamcinolone 0.1% cream to the area twice daily without improvement. Cutaneous examination of the right distal leg revealed an annular red plaque with a raised purpuric border, measuring 13×10 cm (Figure). A biopsy was performed for further evaluation.
What is Your Diagnosis?
Diagnosis: Tinea Incognito
Tinea incognito is a dermatophyte infection of the superficial skin whose morphology differs from the typical tinea corporis due to topical application of an immunosuppressive medication—most commonly a corticosteroid.1
Dermatophytes derive sustenance by metabolizing keratin and infect their hosts by invading keratinized structures such as hair, nails, and the stratum corneum of the skin.2,3 Tinea corporis is transmitted between hosts by skin-to-skin contact, or through fomites.1 Dermatophyte infections are common and between 20% and 25% of the world population is thought to be affected.4 The most common culprit dermatophyte of tinea incognito is Trichophyton rubrum.1
Clinical Presentation
Tinea corporis typically presents on the trunk or extremities as erythematous, annular, papulosquamous lesions with a fine scale, raised borders, and central sparing.1 Application of immunosuppressive medications such as topical corticosteroids, topical pimecrolimus, or topical tacrolimus can significantly alter the clinical appearance of tinea corporis.1 This presentation is termed tinea incognito, and represents approximately 40% of tinea infections.1 Tinea incognito will appear less inflammatory with less scaling than traditional tinea corporis.2 The margin is typically less raised and the lesions may be more pustular and extensive5 (Figures 1A and B).
Pathogenesis
The presence of dermatophytes such as T. rubrum in the stratum corneum elicits an eczematous inflammatory response in the skin layers below.3 Eczematous skin produces keratin less effectively than healthy skin, thereby starving the dermatophyte of sustenance.3 Topical immunosuppressive medications such as corticosteroids, dampen this eczematous response, and in effect, create a more hospitable environment for the dermatophyte to grow.3 Tinea incognito is most likely to occur with application of strong immunosuppressive medications such as fluorinated corticosteroids.2,3 The risk is also increased when these medications are applied under occlusion.2 However, the presentation of tinea corporis can be altered even with application of low-potency steroids such as 1% hydrocortisone cream.2
Pathology
The first step in diagnosing a superficial fungal infection is preparing a potassium hydroxide (KOH) slide preparation for microscopic examination with superficial skin scrapings from the area of concern.6 The presence of hyphae on KOH testing confirms the diagnosis of a dermatophyte infection.6 For typical tinea corporis infections, skin biopsy is rarely indicated.6 However, for patients in whom a superficial fungal skin infection is not suspected or in whom tinea incognito is suspected but not confirmed with examination of a KOH preparation, ruling out other disease processes through biopsy is an appropriate diagnostic approach. Additionally, if Majocchi granuloma (a deep and persistent fungal infection of the hair follicles) is considered in the clinical differential diagnosis, a biopsy may be necessary to identify hyphae within the portion of the hair follicle that would not usually be detected on a superficial skin scraping for a KOH preparation.
The hyaline fungi can be difficult to identify on hematoxylin-eosin (H&E) staining. However, an astute pathologist can sometimes identify the organisms presenting either in cross section or longitudinally between keratinocytes in the stratum corneum. In contrast, using either periodic acid–Schiff (PAS) or Gomori methenamine silver (GMS) stain enables the fungal hyphae to easily be recognized.4
Microscopic examination of the H&E-stained sections reveals mild hyperkeratosis with focal parakeratosis, spongiosis, and neutrophilic microabscesses.4 Perivascular lymphocytes, mild edema, or both may also be present in the dermis (Figures 2A and B).4 Microscopic examination of PAS-stained sections readily demonstrates fungal hyphae in the stratum corneum (Figures 3A and B).
Differential Diagnosis
Tinea incognito represents a diagnostic challenge for clinicians because it commonly mimics other skin disorders. Tinea incognito is most commonly misdiagnosed as eczema, impetigo, lupus erythematosus, rosacea, and psoriasis.1 Other possible diagnoses that could be included in the clinician’s differential include erythema annulare centrifugum, erythema migrans, granuloma annulare, pemphigus foliaceus, and pityriasis rosea.5,7 The skin lesions of tinea incognito can also mimic contact dermatitis, lichen planus, purpura, and seborrheic dermatitis.5
Management
Localized tinea corporis can generally be cured with topical antifungal medications. However, oral antifungals may be necessary for tinea incognito, particularly if they do not resolve with topical therapy.2 Itraconazole, fluconazole, or terbinafine are the first-line agents used to treat tinea incognito.2 These medications tend to concentrate in the keratinized stratum corneum where the dermatophyte resides.2 For tinea incognito, neither a recommended duration of treatment, nor a specific systemic agent has been established.2
Our Patient
The possibility of Majocchi granuloma was entertained; therefore, a lesional skin biopsy from the border of the lesion was performed. Microscopic examination of the H&E-stained sections showed orthokeratosis, and mild acanthosis in the epidermis and a sparse perivascular lymphocytic infiltrate in the dermis (Figures 2A and B). The PAS-stained sections highlighted florid hyphae scattered throughout the stratum corneum (Figures 3A and B). The clinical presentation, history of topical corticosteroid use, and pathology findings confirmed a diagnosis of tinea incognito.
Topical treatment with ketoconazole 2% cream twice daily was initiated. Evaluation after 4 weeks of treatment showed that the lesion had completely resolved.
Conclusion
The incidence of tinea incognito is increasing due to readily available over-the-counter topical corticosteroids, the misuse of strong topical corticosteroids, and self-treating patients with excess corticosteroid ointments from previous dermatoses.3,7 Clinicians should include tinea incognito on their differential diagnosis when a patient presents with annular plaques that are unresponsive to topical corticosteroids. If suspected clinically, a biopsy should be performed with PAS or GMS staining to confirm the diagnosis. In our patient, a definitive diagnosis was made and appropriate treatment was started.
Dr Cox completed medical school at Louisiana State University Health Sciences Center in New Orleans, LA. She looks forward to beginning her intern year at Scripps Mercy Hospital in San Diego, CA.
Dr Cohen is with the department of dermatology at the University of California, San Diego in San Diego, CA.
Disclosure: The authors report not relevant financial relationships.
References
1. Segal D, Wells MM, Rahalkar A, Joseph M, Mrkobrada M. A case of tinea incognito. Dermatol Online J. 2013;19(5):18175.
2. Jacobs JA, Kolbach DN, Vermeulen AH, Smeets MH, Neuman HA. Tinea incognito due to Trichophytom rubrum after local steroid therapy. Clin Infect Dis. 2001;33(12):E142-144.
3. Ive FA, Marks R. Tinea incognito. Br Med J. 1968;3(5611):149-152.
4. Guarner J, Brandt ME. Histopathologic diagnosis of fungal infections in the 21st century. Clin Microbiol Rev. 2011;24(2):247-280.
5. Guenova E, Hoetzenecker W, Schaller M, Röcken M, Fierlbeck G. Tinea incognito hidden under apparently treatment-resistant pemphigus foliaceus. Acta Derm Venereol. 2008;8(3):276-277.
6. Sahoo AK, Mahajan R. Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review. Indian Dermatol Online J. 2016;7(2):77-86.
7. Kim WJ, Kim TW, Mun JH, et al. Tinea incognito in Korea and its risk factors: nine-year multicenter survey. J Korean Med Sci. 2013;28(1):145-151.
An 85-year-old man presented for an itchy rash of his right lower leg for approximately 12 weeks. For the past 3 weeks, he had been applying triamcinolone 0.1% cream to the area twice daily without improvement. Cutaneous examination of the right distal leg revealed an annular red plaque with a raised purpuric border, measuring 13×10 cm (Figure). A biopsy was performed for further evaluation.
What is Your Diagnosis?
An 85-year-old man presented for an itchy rash of his right lower leg for approximately 12 weeks. For the past 3 weeks, he had been applying triamcinolone 0.1% cream to the area twice daily without improvement. Cutaneous examination of the right distal leg revealed an annular red plaque with a raised purpuric border, measuring 13×10 cm (Figure). A biopsy was performed for further evaluation.
What is Your Diagnosis?
To find out the answer and case details, go to page 2
Diagnosis: Tinea Incognito
Tinea incognito is a dermatophyte infection of the superficial skin whose morphology differs from the typical tinea corporis due to topical application of an immunosuppressive medication—most commonly a corticosteroid.1
Dermatophytes derive sustenance by metabolizing keratin and infect their hosts by invading keratinized structures such as hair, nails, and the stratum corneum of the skin.2,3 Tinea corporis is transmitted between hosts by skin-to-skin contact, or through fomites.1 Dermatophyte infections are common and between 20% and 25% of the world population is thought to be affected.4 The most common culprit dermatophyte of tinea incognito is Trichophyton rubrum.1
Clinical Presentation
Tinea corporis typically presents on the trunk or extremities as erythematous, annular, papulosquamous lesions with a fine scale, raised borders, and central sparing.1 Application of immunosuppressive medications such as topical corticosteroids, topical pimecrolimus, or topical tacrolimus can significantly alter the clinical appearance of tinea corporis.1 This presentation is termed tinea incognito, and represents approximately 40% of tinea infections.1 Tinea incognito will appear less inflammatory with less scaling than traditional tinea corporis.2 The margin is typically less raised and the lesions may be more pustular and extensive5 (Figures 1A and B).
Pathogenesis
The presence of dermatophytes such as T. rubrum in the stratum corneum elicits an eczematous inflammatory response in the skin layers below.3 Eczematous skin produces keratin less effectively than healthy skin, thereby starving the dermatophyte of sustenance.3 Topical immunosuppressive medications such as corticosteroids, dampen this eczematous response, and in effect, create a more hospitable environment for the dermatophyte to grow.3 Tinea incognito is most likely to occur with application of strong immunosuppressive medications such as fluorinated corticosteroids.2,3 The risk is also increased when these medications are applied under occlusion.2 However, the presentation of tinea corporis can be altered even with application of low-potency steroids such as 1% hydrocortisone cream.2
Pathology
The first step in diagnosing a superficial fungal infection is preparing a potassium hydroxide (KOH) slide preparation for microscopic examination with superficial skin scrapings from the area of concern.6 The presence of hyphae on KOH testing confirms the diagnosis of a dermatophyte infection.6 For typical tinea corporis infections, skin biopsy is rarely indicated.6 However, for patients in whom a superficial fungal skin infection is not suspected or in whom tinea incognito is suspected but not confirmed with examination of a KOH preparation, ruling out other disease processes through biopsy is an appropriate diagnostic approach. Additionally, if Majocchi granuloma (a deep and persistent fungal infection of the hair follicles) is considered in the clinical differential diagnosis, a biopsy may be necessary to identify hyphae within the portion of the hair follicle that would not usually be detected on a superficial skin scraping for a KOH preparation.
The hyaline fungi can be difficult to identify on hematoxylin-eosin (H&E) staining. However, an astute pathologist can sometimes identify the organisms presenting either in cross section or longitudinally between keratinocytes in the stratum corneum. In contrast, using either periodic acid–Schiff (PAS) or Gomori methenamine silver (GMS) stain enables the fungal hyphae to easily be recognized.4
Microscopic examination of the H&E-stained sections reveals mild hyperkeratosis with focal parakeratosis, spongiosis, and neutrophilic microabscesses.4 Perivascular lymphocytes, mild edema, or both may also be present in the dermis (Figures 2A and B).4 Microscopic examination of PAS-stained sections readily demonstrates fungal hyphae in the stratum corneum (Figures 3A and B).
Differential Diagnosis
Tinea incognito represents a diagnostic challenge for clinicians because it commonly mimics other skin disorders. Tinea incognito is most commonly misdiagnosed as eczema, impetigo, lupus erythematosus, rosacea, and psoriasis.1 Other possible diagnoses that could be included in the clinician’s differential include erythema annulare centrifugum, erythema migrans, granuloma annulare, pemphigus foliaceus, and pityriasis rosea.5,7 The skin lesions of tinea incognito can also mimic contact dermatitis, lichen planus, purpura, and seborrheic dermatitis.5
Management
Localized tinea corporis can generally be cured with topical antifungal medications. However, oral antifungals may be necessary for tinea incognito, particularly if they do not resolve with topical therapy.2 Itraconazole, fluconazole, or terbinafine are the first-line agents used to treat tinea incognito.2 These medications tend to concentrate in the keratinized stratum corneum where the dermatophyte resides.2 For tinea incognito, neither a recommended duration of treatment, nor a specific systemic agent has been established.2
Our Patient
The possibility of Majocchi granuloma was entertained; therefore, a lesional skin biopsy from the border of the lesion was performed. Microscopic examination of the H&E-stained sections showed orthokeratosis, and mild acanthosis in the epidermis and a sparse perivascular lymphocytic infiltrate in the dermis (Figures 2A and B). The PAS-stained sections highlighted florid hyphae scattered throughout the stratum corneum (Figures 3A and B). The clinical presentation, history of topical corticosteroid use, and pathology findings confirmed a diagnosis of tinea incognito.
Topical treatment with ketoconazole 2% cream twice daily was initiated. Evaluation after 4 weeks of treatment showed that the lesion had completely resolved.
Conclusion
The incidence of tinea incognito is increasing due to readily available over-the-counter topical corticosteroids, the misuse of strong topical corticosteroids, and self-treating patients with excess corticosteroid ointments from previous dermatoses.3,7 Clinicians should include tinea incognito on their differential diagnosis when a patient presents with annular plaques that are unresponsive to topical corticosteroids. If suspected clinically, a biopsy should be performed with PAS or GMS staining to confirm the diagnosis. In our patient, a definitive diagnosis was made and appropriate treatment was started.
Dr Cox completed medical school at Louisiana State University Health Sciences Center in New Orleans, LA. She looks forward to beginning her intern year at Scripps Mercy Hospital in San Diego, CA.
Dr Cohen is with the department of dermatology at the University of California, San Diego in San Diego, CA.
Disclosure: The authors report not relevant financial relationships.
References
1. Segal D, Wells MM, Rahalkar A, Joseph M, Mrkobrada M. A case of tinea incognito. Dermatol Online J. 2013;19(5):18175.
2. Jacobs JA, Kolbach DN, Vermeulen AH, Smeets MH, Neuman HA. Tinea incognito due to Trichophytom rubrum after local steroid therapy. Clin Infect Dis. 2001;33(12):E142-144.
3. Ive FA, Marks R. Tinea incognito. Br Med J. 1968;3(5611):149-152.
4. Guarner J, Brandt ME. Histopathologic diagnosis of fungal infections in the 21st century. Clin Microbiol Rev. 2011;24(2):247-280.
5. Guenova E, Hoetzenecker W, Schaller M, Röcken M, Fierlbeck G. Tinea incognito hidden under apparently treatment-resistant pemphigus foliaceus. Acta Derm Venereol. 2008;8(3):276-277.
6. Sahoo AK, Mahajan R. Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review. Indian Dermatol Online J. 2016;7(2):77-86.
7. Kim WJ, Kim TW, Mun JH, et al. Tinea incognito in Korea and its risk factors: nine-year multicenter survey. J Korean Med Sci. 2013;28(1):145-151.
An 85-year-old man presented for an itchy rash of his right lower leg for approximately 12 weeks. For the past 3 weeks, he had been applying triamcinolone 0.1% cream to the area twice daily without improvement. Cutaneous examination of the right distal leg revealed an annular red plaque with a raised purpuric border, measuring 13×10 cm (Figure). A biopsy was performed for further evaluation.
What is Your Diagnosis?
Diagnosis: Tinea Incognito
Tinea incognito is a dermatophyte infection of the superficial skin whose morphology differs from the typical tinea corporis due to topical application of an immunosuppressive medication—most commonly a corticosteroid.1
Dermatophytes derive sustenance by metabolizing keratin and infect their hosts by invading keratinized structures such as hair, nails, and the stratum corneum of the skin.2,3 Tinea corporis is transmitted between hosts by skin-to-skin contact, or through fomites.1 Dermatophyte infections are common and between 20% and 25% of the world population is thought to be affected.4 The most common culprit dermatophyte of tinea incognito is Trichophyton rubrum.1
Clinical Presentation
Tinea corporis typically presents on the trunk or extremities as erythematous, annular, papulosquamous lesions with a fine scale, raised borders, and central sparing.1 Application of immunosuppressive medications such as topical corticosteroids, topical pimecrolimus, or topical tacrolimus can significantly alter the clinical appearance of tinea corporis.1 This presentation is termed tinea incognito, and represents approximately 40% of tinea infections.1 Tinea incognito will appear less inflammatory with less scaling than traditional tinea corporis.2 The margin is typically less raised and the lesions may be more pustular and extensive5 (Figures 1A and B).
Pathogenesis
The presence of dermatophytes such as T. rubrum in the stratum corneum elicits an eczematous inflammatory response in the skin layers below.3 Eczematous skin produces keratin less effectively than healthy skin, thereby starving the dermatophyte of sustenance.3 Topical immunosuppressive medications such as corticosteroids, dampen this eczematous response, and in effect, create a more hospitable environment for the dermatophyte to grow.3 Tinea incognito is most likely to occur with application of strong immunosuppressive medications such as fluorinated corticosteroids.2,3 The risk is also increased when these medications are applied under occlusion.2 However, the presentation of tinea corporis can be altered even with application of low-potency steroids such as 1% hydrocortisone cream.2
Pathology
The first step in diagnosing a superficial fungal infection is preparing a potassium hydroxide (KOH) slide preparation for microscopic examination with superficial skin scrapings from the area of concern.6 The presence of hyphae on KOH testing confirms the diagnosis of a dermatophyte infection.6 For typical tinea corporis infections, skin biopsy is rarely indicated.6 However, for patients in whom a superficial fungal skin infection is not suspected or in whom tinea incognito is suspected but not confirmed with examination of a KOH preparation, ruling out other disease processes through biopsy is an appropriate diagnostic approach. Additionally, if Majocchi granuloma (a deep and persistent fungal infection of the hair follicles) is considered in the clinical differential diagnosis, a biopsy may be necessary to identify hyphae within the portion of the hair follicle that would not usually be detected on a superficial skin scraping for a KOH preparation.
The hyaline fungi can be difficult to identify on hematoxylin-eosin (H&E) staining. However, an astute pathologist can sometimes identify the organisms presenting either in cross section or longitudinally between keratinocytes in the stratum corneum. In contrast, using either periodic acid–Schiff (PAS) or Gomori methenamine silver (GMS) stain enables the fungal hyphae to easily be recognized.4
Microscopic examination of the H&E-stained sections reveals mild hyperkeratosis with focal parakeratosis, spongiosis, and neutrophilic microabscesses.4 Perivascular lymphocytes, mild edema, or both may also be present in the dermis (Figures 2A and B).4 Microscopic examination of PAS-stained sections readily demonstrates fungal hyphae in the stratum corneum (Figures 3A and B).
Differential Diagnosis
Tinea incognito represents a diagnostic challenge for clinicians because it commonly mimics other skin disorders. Tinea incognito is most commonly misdiagnosed as eczema, impetigo, lupus erythematosus, rosacea, and psoriasis.1 Other possible diagnoses that could be included in the clinician’s differential include erythema annulare centrifugum, erythema migrans, granuloma annulare, pemphigus foliaceus, and pityriasis rosea.5,7 The skin lesions of tinea incognito can also mimic contact dermatitis, lichen planus, purpura, and seborrheic dermatitis.5
Management
Localized tinea corporis can generally be cured with topical antifungal medications. However, oral antifungals may be necessary for tinea incognito, particularly if they do not resolve with topical therapy.2 Itraconazole, fluconazole, or terbinafine are the first-line agents used to treat tinea incognito.2 These medications tend to concentrate in the keratinized stratum corneum where the dermatophyte resides.2 For tinea incognito, neither a recommended duration of treatment, nor a specific systemic agent has been established.2
Our Patient
The possibility of Majocchi granuloma was entertained; therefore, a lesional skin biopsy from the border of the lesion was performed. Microscopic examination of the H&E-stained sections showed orthokeratosis, and mild acanthosis in the epidermis and a sparse perivascular lymphocytic infiltrate in the dermis (Figures 2A and B). The PAS-stained sections highlighted florid hyphae scattered throughout the stratum corneum (Figures 3A and B). The clinical presentation, history of topical corticosteroid use, and pathology findings confirmed a diagnosis of tinea incognito.
Topical treatment with ketoconazole 2% cream twice daily was initiated. Evaluation after 4 weeks of treatment showed that the lesion had completely resolved.
Conclusion
The incidence of tinea incognito is increasing due to readily available over-the-counter topical corticosteroids, the misuse of strong topical corticosteroids, and self-treating patients with excess corticosteroid ointments from previous dermatoses.3,7 Clinicians should include tinea incognito on their differential diagnosis when a patient presents with annular plaques that are unresponsive to topical corticosteroids. If suspected clinically, a biopsy should be performed with PAS or GMS staining to confirm the diagnosis. In our patient, a definitive diagnosis was made and appropriate treatment was started.
Dr Cox completed medical school at Louisiana State University Health Sciences Center in New Orleans, LA. She looks forward to beginning her intern year at Scripps Mercy Hospital in San Diego, CA.
Dr Cohen is with the department of dermatology at the University of California, San Diego in San Diego, CA.
Disclosure: The authors report not relevant financial relationships.
References
1. Segal D, Wells MM, Rahalkar A, Joseph M, Mrkobrada M. A case of tinea incognito. Dermatol Online J. 2013;19(5):18175.
2. Jacobs JA, Kolbach DN, Vermeulen AH, Smeets MH, Neuman HA. Tinea incognito due to Trichophytom rubrum after local steroid therapy. Clin Infect Dis. 2001;33(12):E142-144.
3. Ive FA, Marks R. Tinea incognito. Br Med J. 1968;3(5611):149-152.
4. Guarner J, Brandt ME. Histopathologic diagnosis of fungal infections in the 21st century. Clin Microbiol Rev. 2011;24(2):247-280.
5. Guenova E, Hoetzenecker W, Schaller M, Röcken M, Fierlbeck G. Tinea incognito hidden under apparently treatment-resistant pemphigus foliaceus. Acta Derm Venereol. 2008;8(3):276-277.
6. Sahoo AK, Mahajan R. Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review. Indian Dermatol Online J. 2016;7(2):77-86.
7. Kim WJ, Kim TW, Mun JH, et al. Tinea incognito in Korea and its risk factors: nine-year multicenter survey. J Korean Med Sci. 2013;28(1):145-151.
Diagnosis: Tinea Incognito
Tinea incognito is a dermatophyte infection of the superficial skin whose morphology differs from the typical tinea corporis due to topical application of an immunosuppressive medication—most commonly a corticosteroid.1
Dermatophytes derive sustenance by metabolizing keratin and infect their hosts by invading keratinized structures such as hair, nails, and the stratum corneum of the skin.2,3 Tinea corporis is transmitted between hosts by skin-to-skin contact, or through fomites.1 Dermatophyte infections are common and between 20% and 25% of the world population is thought to be affected.4 The most common culprit dermatophyte of tinea incognito is Trichophyton rubrum.1
Clinical Presentation
Tinea corporis typically presents on the trunk or extremities as erythematous, annular, papulosquamous lesions with a fine scale, raised borders, and central sparing.1 Application of immunosuppressive medications such as topical corticosteroids, topical pimecrolimus, or topical tacrolimus can significantly alter the clinical appearance of tinea corporis.1 This presentation is termed tinea incognito, and represents approximately 40% of tinea infections.1 Tinea incognito will appear less inflammatory with less scaling than traditional tinea corporis.2 The margin is typically less raised and the lesions may be more pustular and extensive5 (Figures 1A and B).
Pathogenesis
The presence of dermatophytes such as T. rubrum in the stratum corneum elicits an eczematous inflammatory response in the skin layers below.3 Eczematous skin produces keratin less effectively than healthy skin, thereby starving the dermatophyte of sustenance.3 Topical immunosuppressive medications such as corticosteroids, dampen this eczematous response, and in effect, create a more hospitable environment for the dermatophyte to grow.3 Tinea incognito is most likely to occur with application of strong immunosuppressive medications such as fluorinated corticosteroids.2,3 The risk is also increased when these medications are applied under occlusion.2 However, the presentation of tinea corporis can be altered even with application of low-potency steroids such as 1% hydrocortisone cream.2
Pathology
The first step in diagnosing a superficial fungal infection is preparing a potassium hydroxide (KOH) slide preparation for microscopic examination with superficial skin scrapings from the area of concern.6 The presence of hyphae on KOH testing confirms the diagnosis of a dermatophyte infection.6 For typical tinea corporis infections, skin biopsy is rarely indicated.6 However, for patients in whom a superficial fungal skin infection is not suspected or in whom tinea incognito is suspected but not confirmed with examination of a KOH preparation, ruling out other disease processes through biopsy is an appropriate diagnostic approach. Additionally, if Majocchi granuloma (a deep and persistent fungal infection of the hair follicles) is considered in the clinical differential diagnosis, a biopsy may be necessary to identify hyphae within the portion of the hair follicle that would not usually be detected on a superficial skin scraping for a KOH preparation.
The hyaline fungi can be difficult to identify on hematoxylin-eosin (H&E) staining. However, an astute pathologist can sometimes identify the organisms presenting either in cross section or longitudinally between keratinocytes in the stratum corneum. In contrast, using either periodic acid–Schiff (PAS) or Gomori methenamine silver (GMS) stain enables the fungal hyphae to easily be recognized.4
Microscopic examination of the H&E-stained sections reveals mild hyperkeratosis with focal parakeratosis, spongiosis, and neutrophilic microabscesses.4 Perivascular lymphocytes, mild edema, or both may also be present in the dermis (Figures 2A and B).4 Microscopic examination of PAS-stained sections readily demonstrates fungal hyphae in the stratum corneum (Figures 3A and B).
Differential Diagnosis
Tinea incognito represents a diagnostic challenge for clinicians because it commonly mimics other skin disorders. Tinea incognito is most commonly misdiagnosed as eczema, impetigo, lupus erythematosus, rosacea, and psoriasis.1 Other possible diagnoses that could be included in the clinician’s differential include erythema annulare centrifugum, erythema migrans, granuloma annulare, pemphigus foliaceus, and pityriasis rosea.5,7 The skin lesions of tinea incognito can also mimic contact dermatitis, lichen planus, purpura, and seborrheic dermatitis.5
Management
Localized tinea corporis can generally be cured with topical antifungal medications. However, oral antifungals may be necessary for tinea incognito, particularly if they do not resolve with topical therapy.2 Itraconazole, fluconazole, or terbinafine are the first-line agents used to treat tinea incognito.2 These medications tend to concentrate in the keratinized stratum corneum where the dermatophyte resides.2 For tinea incognito, neither a recommended duration of treatment, nor a specific systemic agent has been established.2
Our Patient
The possibility of Majocchi granuloma was entertained; therefore, a lesional skin biopsy from the border of the lesion was performed. Microscopic examination of the H&E-stained sections showed orthokeratosis, and mild acanthosis in the epidermis and a sparse perivascular lymphocytic infiltrate in the dermis (Figures 2A and B). The PAS-stained sections highlighted florid hyphae scattered throughout the stratum corneum (Figures 3A and B). The clinical presentation, history of topical corticosteroid use, and pathology findings confirmed a diagnosis of tinea incognito.
Topical treatment with ketoconazole 2% cream twice daily was initiated. Evaluation after 4 weeks of treatment showed that the lesion had completely resolved.
Conclusion
The incidence of tinea incognito is increasing due to readily available over-the-counter topical corticosteroids, the misuse of strong topical corticosteroids, and self-treating patients with excess corticosteroid ointments from previous dermatoses.3,7 Clinicians should include tinea incognito on their differential diagnosis when a patient presents with annular plaques that are unresponsive to topical corticosteroids. If suspected clinically, a biopsy should be performed with PAS or GMS staining to confirm the diagnosis. In our patient, a definitive diagnosis was made and appropriate treatment was started.
Dr Cox completed medical school at Louisiana State University Health Sciences Center in New Orleans, LA. She looks forward to beginning her intern year at Scripps Mercy Hospital in San Diego, CA.
Dr Cohen is with the department of dermatology at the University of California, San Diego in San Diego, CA.
Disclosure: The authors report not relevant financial relationships.
References
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2. Jacobs JA, Kolbach DN, Vermeulen AH, Smeets MH, Neuman HA. Tinea incognito due to Trichophytom rubrum after local steroid therapy. Clin Infect Dis. 2001;33(12):E142-144.
3. Ive FA, Marks R. Tinea incognito. Br Med J. 1968;3(5611):149-152.
4. Guarner J, Brandt ME. Histopathologic diagnosis of fungal infections in the 21st century. Clin Microbiol Rev. 2011;24(2):247-280.
5. Guenova E, Hoetzenecker W, Schaller M, Röcken M, Fierlbeck G. Tinea incognito hidden under apparently treatment-resistant pemphigus foliaceus. Acta Derm Venereol. 2008;8(3):276-277.
6. Sahoo AK, Mahajan R. Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review. Indian Dermatol Online J. 2016;7(2):77-86.
7. Kim WJ, Kim TW, Mun JH, et al. Tinea incognito in Korea and its risk factors: nine-year multicenter survey. J Korean Med Sci. 2013;28(1):145-151.
