Diagnosing A Patient With Painful Cracks On Both Soles

A 12-year-old boy presented with painful cracks on both soles. You are the third doctor he and his parents have seen. The patient’s mother is upset that the rash keeps returning and the father is skeptical about healthcare providers who haven’t cured the problem. The patient is anxious and afraid of what you will do to treat him. He has tried numerous creams and sprays, but nothing works for long. The family has changed laundry soap, softeners and shoes, but the cracks come back.

The patient has no significant past medical history other than asthma. The patient’s mother has sensitive skin and the father has seasonal allergies. The family has had the same cat and a dog for over five years. The patient is doing well in school and denies any food intolerances. He admits drinking soda pop twice daily.

The patient often swims in the family pool. Although the patient’s feet are dry at the time of the visit, both his sneakers and cotton socks are damp. Dad reports his son’s feet are sweaty but has noticed no foot odor. The patient always takes off his shoes and socks indoors.

What Does The Physical Examination Reveal?

The cracks started over two years ago and are limited to the soles and toe pads of both feet. The fissures and cracks spare the arches and sulci. There is mild erythema adjacent to the some of the fissures and several larger cracks are topped with dry crusts. Most of the surface cracks are generally arranged transversely along the edges of the soles. The thicker skin areas of the soles have a glazed appearance. There are many fine white superficial cracks between the linear fissures.

Key Questions To Consider

1. Which differential diagnoses should you consider?
2. What is the primary impression?
3. What are the distinctive features of this patient’s soles?
4. How can patients best manage this condition?

Answering The Key Diagnostic Questions

1. Tinea pedis, allergic contact dermatitis, atopic dermatitis, pedal hyperhidrosis, ichthyosis
2. Juvenile plantar dermatosis
3. This patient has cracks on soles and toe pads, mild erythema adjacent to some fissures, and several larger cracks topped with dry crusts. Most surface cracks are generally transverse along the edges of the soles.
4. Treatment includes managing the fissure symptoms with anti-inflammatory topicals and subsequently addressing transepidermal water loss. 

Parsing The Differential Diagnoses

Whenever scaling is evident on the soles, it is always prudent to rule out tinea pedis. However, tinea is less likely in young patients because of their thinner plantar skin. One can easily rule out a superficial dermatophyte infection by collecting scales for microscopic examination in the clinic or sending the scales to the pathologist for analysis with periodic acid-Schiff (PAS) or Giemsa stains. If the findings are positive, a mycologist can identify the fungal species.

The differential diagnosis list should also include allergic contact dermatitis, atopic dermatitis and ichthyosis.¹ An allergist can confirm an allergy to the chemical components of the shoes with patch testing but careful clinical observation is often sufficient. Shoe contact dermatitis typically has a symmetric distribution that spares the toe webs. The rash of contact dermatitis should closely correlate to the points of contact.

With atopic eczema, the patient or a family member is likely to have a history of sensitive skin, allergic rhinitis, hay fever or asthma. Atopic eczema symptoms include burning, stinging or simple discomfort. A flexor surface distribution of rashes favors an atopic eczema diagnosis. In contrast to allergic contact dermatitis, itching is usually modest or absent.

Pedal hyperhidrosis is not uncommon with active children who wear occlusive footwear and it may be an aggravating factor in all types of eczema. Excessive sweating of the palms and soles is amplified by sympathetic stimulation of the eccrine ducts. Caffeinated beverages increase sympathetic tone, stimulating eccrine sweating of the palms and soles.

Although ichthyosis can be a differential diagnosis, there usually is a family history of the keratoderma and/or nail dystrophy. Psoriasis in children tends to present in the guttate form following a streptococcal pharyngitis. Typically, psoriasis affects the extensor surfaces and would be accompanied by itchy dry plaques on the upper extremities or scalp.

In recalcitrant cases when a specific diagnosis remains elusive, performing a simple 3-mm punch biopsy would easily differentiate between fungus infection and psoriasis. However, this biopsy may not be able to distinguish between the various subtypes of eczema that share similar histopathological features. Consultation with a pediatric dermatologist is always a good option.

What You Should Know About Juvenile Plantar Dermatosis

The primary clinical impression for this patient is juvenile plantar dermatosis. Juvenile plantar dermatosis is also known as “sweaty sock syndrome” and “wet-foot, dry-foot syndrome,” but it is best to think of it as a special form of irritant contact dermatitis stemming from repeated cycles of moisture exposure followed by rapid drying. The repetitive cycles of wetting, either from water exposure or sweat, followed by rapid drying in low humidity conditions lead to the reduced moisture content and subsequent cracking of the thicker plantar skin.

Dehydrated skin is less flexible and less compliant with the shear forces of walking, thus creating cracks and fissures. Normal skin cells bind three times their weight in water within their surface lipids and proteins such as ceramide and filaggrin.¹ One may consider juvenile plantar dermatosis a special presentation of atopic eczema. Patients with atopic eczema have a genetic mutation of their filaggrin. This makes patients with atopic eczema more susceptible to sources of irritant contact dermatitis as well as viral and bacterial infections.

Normal skin functions best when the humidity is 60 percent but rapidly loses its water content when exposed to low humidity situations like removal of occlusive foot gear in centrally heated homes or lying in the sun after swimming. The ambient humidity of centrally heated homes is typically 35 percent or less. When the skin loses more than 10 percent of its water content, it tends to crack like drying mud. Cracked corneocytes release inflammatory cytokines like tumor necrosis-alpha and interleukin-1, triggering cycles of inflammation.¹  

Relevant Keys To Treatment

Since juvenile plantar dermatosis is primarily driven by cutaneous genetic imperfections, management is a process of putting out the fire and then implementing long-term prevention. One can treat deep, painful fissures with lidocaine ointment. Paring back the steep sides of the fissure and covering with moleskin helps to stop painful motion along the fissures, and facilitates wound repair.

Triamcinolone (Kenalog, Bristol-Myers Squibb) gets the red out. Applications of mid-potency 0.1% triamcinolone ointment two to three times per day should help to control the acute symptoms throughout the first few weeks. In the long-term, patients can apply intermittent 0.025% triamcinolone cream or lotion on the weekends to help maintain long-term remission. Thankfully, appropriate long-term use of low- or mid-potency topical corticosteroids does not cause hypothalamic-pituitary-adrenal suppression in infants and children.² The overzealous use of topical steroids can lead to localized side effects such as skin atrophy, hypopigmentation or striae.¹ Therefore, it is always prudent to discuss these potential adverse drug reactions.

Rebalancing cutaneous water and lipids reduces transepidermal water loss.³ Twice-a-day applications of emollients, immediately after shoe removal, helps prevent the thicker skin from drying out too rapidly and reduces the skin’s susceptibility to irritant reactions. Lipid applications not only improve skin hydration but improve elasticity and reduce erythema. Eucerin (Beiersdorf AG) and Cetaphil (Galderma) creams are good examples of emollients that patients can use liberally in conjunction with topical corticosteroids.¹ Naturally, patients should avoid excessive bathing with soap and hot water. Encourage patients or their parents in this case to assess the humidity of the environment and optimize it to be above 40 percent. A furnace humidifier or simply boiling water on the stove can increase home humidity. A simple economic humidity monitor is quite useful to manage home humidity. The humidity in centrally heated homes in the winter can drop below 25 percent.  

Once the painful cracks resolve, prevention is the key to reduce the chance of recurrent episodes. Wearing foot gear indoors discourages rapid drying of the soles. Teach patients to apply emollients immediately after removing shoes and socks. In addition, liberal application of emollients after bathing or swimming helps to counter the drying effects of immersion. Taking the time to educate both the parents and the patient will help develop their understanding of the challenges of sensitive skin, and encourage their adherence to a comprehensive management plan.

Dr. Bodman is a retired Associate Professor at the Kent State University College of Podiatric Medicine. He is board-certified by the American Board of Podiatric Medicine.

References

1.     Weston WL, Levy ML, Corona R. Contact dermatitis in children. UpToDate. Available at https://www.uptodate.com/contents/contact-dermatitis-in-children . Published March 07, 2017. Accessed Sept. 25, 2017.
2.     Ellison JA, Patel L, Ray DW, et al. Hypothalamic-pituitary-adrenal function and glucocorticoid sensitivity in atopic dermatitis. Pediatrics. 2000; 105(4 Pt1):794.
3.     Mojumdar EH, Pham QD, Topgaard D, Sparr E. Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum. Sci Rep. 2017;7(1):15712.