Juvenile Plantar Dermatosis (Sweaty Sock Syndrome)
(DDX Tinea Pedia, Corynebacteria, Psoriasis)

The girl described in the vignette has features of atopic dermatitis involving the feet, also known as juvenile plantar dermatosis. It is a chronic condition that persists year round and may be associated with atopic dermatitis. During ‘flares’ typically, the plantar surface of the foot, toes and anterior portion exhibit:

• Erythema of the soles, usually limited to the forefoot, sometimes shiny and glazed
• thickening of the skin (with resultant prominence of skin creases)
• mild scaling
• painful hyperkertosis
• occasionally, painful fissures, that are accentuated in the flexural creases of the toes and on the weight bearing areas

Between inflammatory flares, is a dry, ‘non-inflammatory phase’: dry, scaly and fissured skin on the anterior third of the soles of the feet, the heels, and the toes. Erythema is absent. This phase closely resembles tinea pedis, though web spaces and toenails are usually spared in JPD.
Who?

• cause of juvenile plantar dermatosis is unknown
• believed to be a manifestation of atopic dermatitis that is unique in children ages 4 to 7 years, more common in boys
• rarely is observed before the age of 1 year and disappears before puberty.

Contributing factors:

• Excessive hydration of the feet (wearing occlusive shoes or synthetic socks)
• Repeated cycles of hydration during the day (when shoes are worn) followed by dehydration at night (when shoes are removed), causing rapid drying of the skin.
• Most severe during the summer months

Management

• Wear fresh cotton socks with breathable leather shoes or sandals; try a second boot liner on alternate days.
• During flares: mid-potency topical corticosteroid (eg, triamcinolone) is indicated twice daily to inflamed areas to reduce hyperkeratosis and fissuring. Topical calcineurin inhibitors  may also be used for flares (may interfere less with barrier repair vs steroids)
• Occasionally, higher potency agents are required.
• If significant fissuring has already occurred, apply methylmethacrylate glue to ‘caulk’ the fissure while intensifying the rest of the management strategy.
• Avoiding occlusive footwear and wearing absorptive socks may be beneficial for some patients.
• Application of an ointment-based emollient as soon as shoes are removed and at bedtime may prevent cracking due to repeated cycles of hydration and dehydration.
• The non-inflammatory, dry phase does not require topical therapy; in fact, corticosteroids may interfere with epidermal repair.
• Usually improves dramatically during puberty. Rarely persists into adulthood

DDX - A number of skin disorders may involve the plantar surface of the foot and be confused with atopic dermatitis:
Pitted keratolysis is the result of infection with Corynebacterium sp.

• often asymptomatic, though may be associated with unpleasant foot odor, excessive sweating of the feet, or occasionally, pain.
• Lesions are multiple small, superficial pits that may coalesce into large erosions.
• Lesions usually are skin-colored, but rarely become yellow or brown or surrounded by a violaceous ring.
• Application of aluminum chloride (to reduce moisture) or a topical antibiotic, such as clindamycin (to reduce odor), are effective.
• may benefit from avoiding occlusive footwear and wearing absorptive socks.

Psoriasis

• When it affects the feet, psoriasis produces erythematous, scaling plaques that may fissure.
• The scale is thick and adherent, and when removed, pinpoint areas of hemorrhage may be observed (Auspitz sign).
• A number of treatments are available for psoriasis, including calcipotriene, a vitamin D3 analog that inhibits epidermal proliferation. J

Tinea Pedis

• Juvenile plantar dermatosis often is confused with tinea pedis. The latter condition, however, occurs infrequently before puberty, although the older the child, the more important it is to obtain fungal cultures to rule this out.
• In addition, although widespread involvement of the plantar surface of the feet is possible with tinea, most patients exhibit interdigital maceration, scaling , and fissuring. Web spaces are toenails are usually spared in JPD and involved in tinea. Tinea pedis is also usually unilateral. Tinea pedis may be treated with an imidazole antifungal such as miconazole nitrate.

References:
Consultant for Pediatricians. March 2009.