Proposing an Algorithm to Treat Dystrophic Toenails

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Nail pathology can be an indication of systemic underlying disease, but can also have etiologies that include biomechanical abnormalities, psoriasis, fungal infection, physiologic disturbances, deficiencies in vitamins and minerals, or a secondary bacterial infection. Half of the nail disease seen in the office is onychomycosis (Figure 1).¹Other issues that can present uniquely in the toenails include disappearing nail bed, onychogryphosis, onychomadesis, and retronychia. These entities fall under the umbrella term “nail dystrophy,” which can be visually similar to onychomycosis. This article reviews various nail maladies and presents an algorithm to assist the clinician in the office.

A Guide to Nail Disease States

Psoriasis. Psoriasis can affect the skin, nails, and joints. Classically, psoriatic nail disease consists of onycholysis, salmon (oil) spots (discolored areas that represent nail bed psoriasis), an irregular pitting pattern, and onychauxis (Figure 2). Koebner phenomenon, or the appearance of lesions at the site of injury, can also occur in the nails and may manifest in an asymmetric presentation. If a patient presents with an onychomycosis-like nail involvement and has failed oral antifungals, the clinician should consider a diagnosis of psoriatic nail disease. Also, if psoriatic plaques and nail dystrophy are present, it does not automatically lead to a diagnosis of psoriatic nail disease.¹ Confirmatory lab testing, such as periodic acid-Schiff (PAS) staining and polymerase chain reaction (PCR), is essential to achieve the correct diagnosis. In addition to the nail changes, periungual erythema may be present. Patients may also present with the arthritic component of psoriasis, which may manifest in dactylitis of the digits (sausage toes), enthesitis of the Achilles tendon, and distal interphalangeal joint involvement.

Management of nail psoriasis involves reducing the inflammatory response. Treatments include injection of a corticosteroid, such as triamcinolone, into the nail matrix and the use of topical tazarotene, oral acitretin, or some of the systemic biologic agents.

Lichen planus of the nail. Lichen planus is an idiopathic T cell-mediated inflammatory condition that affects the skin, hair, nails, and mucous membranes. This condition more commonly affects fingernails but, in my practice, I have found toenail disease related to lichen planus to be more common than the literature describes.¹

Lichen planus usually affects several nails. The nails become thin, rough (trachyonychia), ridged longitudinally (onychorrhexis), and fissured, and can develop a dorsal wing formation of the proximal nail fold, or pterygium formation, over the nail plate. If the matrix damage from lichen planus is not addressed, these nail findings become permanent scarred reminders of the skin disease that may resolve. Clinicians may manage nail lichen planus with injectable steroids, such as triamcinolone, into the nail matrix.

What You Should Know About Other Signs of Nail Dystrophy

Beau lines. Beau lines are transverse palpable grooves that run along the nail and represent periods of arrest in nail plate growth. The growth arrest is attributed to prior severe systemic illness or trauma.² Each insult to the nail matrix is eventually followed by recovery and continuation of nail growth.³ This generates the grooved appearance of the nail.³

Beau lines most commonly occur bilaterally, affecting all 20 digits, as a result of systemic illnesses and drugs. In some cases, they can occur in isolation when trauma or isolated digital inflammation is involved, specifically trauma to the hand, wrist, elbow, or foot. These traumas can include manicures, pedicures, and shoe trauma, as well as fractures to the hand, wrist, or elbow.⁴ Some more common systemic conditions linked to Beau lines are zinc deficiency, erythroderma, psoriasis, eczema, pemphigus, Raynaud disease, hyperpyrexia, acute stress, rheumatic fever, malaria, myocardial infarction, oral retinoid treatment, and chemotherapy treatment.^4-6 Considering that fingernails grow at a rate of about 3 mm per month and toenails about 1 mm to 2 mm per month, the length of time of the pathology can be gauged by measuring the distance from the proximal nail fold to the distal groove of the Beau line.^4,5

During a pedicure, the process of manipulating the cuticle may lead to Beau lines, or depressions of the nail plate that are parallel to the proximal nail fold. Also, scraping of the hyponychium can lead to onycholysis, which provides a pocket for dermatophyte infection to take hold.

Onychorrhexis. Onychorrhexis is described as nail thickening and ridging in a longitudinal pattern.⁷ Features of onychorrhexis can vary from a small number of isolated ridges to deep involvement covering up to 70% of the nail. Longitudinal splitting can be superficial or deep.⁸ Twenty percent of people have reported signs of brittle nails. Women are more frequently affected, and the incidence is 15% higher in patients older than age 60 years.⁸

Onychorrhexis is most commonly caused by trauma from exogenous sources, lichen planus, and systemic pathologies. All causes are related to disorganized regulation of keratin in the nail matrix.⁹ Exogenous traumas, such as chemical exposure, frequent hand washing, and pedicures, are among the more common causes.⁹

Furthermore, onychorrhexis is a hallmark feature of lichen planus. Diagnosis of lichen planus can be inferred from a large midline indentation or ridging, but this finding can be normal in older patients.⁷

Systemic findings include anemia and arteriosclerosis, which decrease the oxygen content of the matrix and lead to keratin disorganization.¹⁰ Other metabolic causes include rheumatoid arthritis, hyperthyroidism, hypothyroidism, anorexia nervosa, bulimia nervosa, and Raynaud disease.^9-11 It has been theorized that sulfur content is diminished in patients with onychorrhexis. This leads to fewer disulfide bonds in proteins that form keratin fibrils.¹⁰ Treatment of onychorrhexis is dependent on the underlying source of the problem.

Leukonychia. Leukonychia describes a white discoloration of the nail plate, which presents clinically as leukonychia totalis, leukonychia partialis, leukonychia striata, and leukonychia punctata.¹² Leukonychia totalis involves whiteness of the entire nail and has commonly been described as a hereditary condition that is autosomal dominant.¹³ Leukonychia partialis involves only a portion of the nail and is more commonly associated with a systemic disease or trauma. However, both conditions can be acquired or inherited.¹⁴ Although the exact pathophysiologic mechanism of leukonychia totalis is unclear, it is thought to be due to abnormal keratinization of the nail plate.¹⁵

Leukonychia can be associated with several disease states and toxicities, including renal disease, liver disease, cardiac disease, and arsenic intoxication.¹⁶ When associated with these disease states, it will often present as 1 of 4 nail patterns: Mees lines, Terry nails, half-and-half (or Lindsay nails), and Muehrcke lines.¹⁶

Mees lines are transverse, nonblanching, nonpalpable, white bands that run parallel to the lunula.¹⁷ These lines are associated with arsenic poisoning, certain chemotherapeutic drugs, and Hodgkin lymphoma.¹⁷

Indistinguishable from the lunula, Terry nails involve whiteness of almost the entire nail, with a sparing of the distal 0.5 mm to 3.0 mm.¹⁸ This pattern can occur with congestive heart failure, chronic renal failure, hepatic disease, diabetes, and idiopathically.¹⁸

Lindsay nails present with the proximal one-third to one-half of the nail being white, with the distal aspect being reddish-brown.¹⁹ This arrangement is seen in patients with chronic kidney disease and renal failure.¹⁹

Muehrcke lines are multiple, white, parallel bands that are separated by normal pink tissue and present on all nails bilaterally.²⁰ These lines are characteristic in individuals who have chronic hypoalbuminemia associated with hepatic disease and cirrhosis.²⁰ For these disease-associated manifestations of leukonychia, correction of the underlying disease may lead to normalization of the nails.²¹

Longitudinal melanonychia (LM). LM presents as a brown/ black longitudinal band that extend from the nail matrix to the distal edge of the nail plate.²² LM is caused by either melanocytic activation or melanocyte proliferation.²³ Most cases of LM are caused by a benign process, such as melanocytic activation or melanocytic nevi; however, another cause is malignant melanoma.²³ Nail melanomas are most commonly seen between ages 50 and 60 years and should be examined further if LM presents during this time period.²² Age, along with factors such as the lesion being greater than 6 mm, location (the thumb, great toe, and index finger are most common), and skin color require more in-depth examination.²² If LM is present on 1 digit, perform further examination because there is a higher incidence of malignancy.²² Performing an in-depth and thorough patient history is the first step in diagnosing malignant or benign LM. Medication and social and medical history can indicate trauma or drug use as the cause and rule out malignancy.

A helpful tool in diagnosing whether LM is malignant or benign is the dermatoscope. Dermatoscopy allows the visualization of lesions that are not normally seen and will reduce the number of unnecessary biopsies for patients with LM. Dermatoscopy cannot visualize the nail matrix where the disease begins.²⁴ For this reason, nail biopsies are the gold standard to determine benign vs malignant LM. Many different techniques can be performed; however, it is important to obtain a nail matrix specimen because this is where the nail grows from and where the disease begins.

If the lesion is benign LM, the course of action is reassurance and periodic evaluation. However, if found to be malignant, surgical excision is indicated.²⁵ Treatment includes the excision of 5-mm to 10-mm borders with or without bone resection and possible lymph node resection. More aggressive treatment requires amputation at the appropriate joint level.²²

An Algorithm for Nail Evaluation: Targeted to Expanded

Clinicians are faced with unique factors causing toenail dystrophy. The following algorithm aims to assist the clinician in the office when presented with a nail that may not have a fungal infection. Ultimately, I recommend focusing on the nail itself and then expanding out to identify any pedal issues followed by any systemic causes that could be creating nail dystrophy.

1. Assess the nail unit characteristics. How many nails are dystrophic (Figure 3)? Is it symmetrical or bilateral? What is the shape of the nail? Does the nail “stop” growing due to the shape of the distal digit like in a disappearing nail bed? What color(s) are present (red, black, green, yellow, brown, white)? What is the quality of the nail plate (brittle, peeling, dry)? Is the cuticle present? What is the quality of the periungual skin (scaly, erythematous, pruritic)? How does the nail plate and bed appear when viewed distally instead of looking down on it? Are there Beau lines or is onychorrhexis or pigmentation present?

2. Assess the anatomy and any underlying biomechanical issues. Anatomically, what is present that could be affecting the nails (hammer toes, hallux valgus, hallux limitus/rigidus, long second toe, adductovarus deformity of the fifth toe)? Is there a correlation between the nail issue and the anatomy and/ or biomechanics?

3. Assess for an internal or an external cause. Is there a history of trauma, inflammatory skin disease (psoriasis, eczema), or chemotherapeutic agents that may contribute to nail issues (onychocryptosis to pigmentation changes)? Does the patient get pedicures regularly, including gel nail polish or application of acrylic nails? Has the patient had numerous nail surgeries over the years that have narrowed the nail plate width? Or has the patient had repeated total nail avulsions that have caused the nail bed to disappear? Does the patient “pick” their nails and periungual skin?

4. Perform laboratory testing or a biopsy of the nail unit. Once the above questions have been assessed, laboratory nail testing may be performed to refine the diagnosis. This may involve PAS staining, PCR testing, potassium hydroxide procedure, and fungal culture, or a punch biopsy of the nail unit. A simple punch biopsy of the nail unit can be used to identify the cause of LM, nail psoriasis, proximal subungual onychomycosis, various skin cancers affecting the nail, subungual verrucae, and other nail tumors.

5. Formulate a treatment plan. Treatment options will depend on the results of the laboratory testing or clinical assessment. If shoe gear is an issue, then a discussion on proper shoe size, depth, and type may be warranted. Surgical intervention of either the nail unit or anatomic issue, such as adductovarus deformity of the fifth toe, may be appropriate. See above for therapeutic options for nail involvement in inflammatory skin conditions. The following section describes over-the-counter options for onychodystrophy of various causes.

Nonprescription Treatment Options

Onychodystrophic nails are typically dry in appearance. A topical product that has been on the over-the-counter market for several years is DermaNail (Summers Labs). It is described as a nail conditioner for brittle nails that is applied topically once a day (Figure 4).

In addition, if cosmesis is a concern for the patient, Keryflex (Podiatree) nail resin may be applied to camouflage and protect the nail unit. Keryflex has been used to cover nail fungus and various other nail dystrophies.

I no longer recommend biotin supplements due to the US Food and Drug Administration’s statement on possible interference with laboratory testing.²⁶ It significantly interferes with laboratory studies, causing either a falsely high or low result depending on the test.²⁶ Biotin, or vitamin B7, is used in laboratory studies due to its ability to bind to specific proteins. For example, biotin is a part of the laboratory test for detection of troponin T, a marker of cardiac damage.²⁶ Both patients and physicians may be unaware of the potential biotin interference in laboratory tests. Patients may not even realize that the “hair, skin, and nails” supplement they bought at the drugstore contains higher than recommended doses of biotin or has biotin at all. If your patient is taking biotin supplements, make them aware that many laboratory tests, including but not limited to cardiovascular diagnostic tests and hormone tests that use biotin technology, are potentially affected, and incorrect test results may be generated if there is biotin in the patient’s specimen.²⁶

Final Thoughts

Nail pathology is a staple condition evaluated by clinicians daily. However, the multitude of potential etiologies, especially those that originate outside the foot itself, make clear workup and treatment a necessity.

References

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