ANSWER
The correct answer is juvenile plantar dermatosis (JPD; choice “b”). It is a condition related to having thin, dry, hyperreactive skin exposed to friction, wetting and drying, and constant exposure to the nonpermeable surfaces of shoes.
Pitted keratolysis (choice “a”) is a condition caused by sweating and increased warmth. The plantar keratin is broken down with the help of bacteria that overgrow in affected areas; this eventuates in focal loss of keratin in arcuate patterns. It is quite unlikely to occur prior to puberty.
Tinea pedis (choice “c”) is dermatophytosis, or fungal infection of the foot. It is also unusual prior to puberty, unlikely to present in the manner seen in this case, and likely to have responded at least partially to antifungal creams.
Psoriasis (choice “d”) seldom presents with fissuring, would not be confined to weight-bearing surfaces, and would probably have involved other areas, such as the scalp, elbows, knees, or nails.
DISCUSSION
JPD, also known as juvenile plantar dermatitis, is found almost exclusively on the weight-bearing surfaces of the feet of children ages 4 to 8—mostly boys, for whom this represents a manifestation of the atopic diathesis. Seen mostly in the summer, it is thought to be triggered by friction, wetting and drying, and shoe selection (ie, plastic rather than leather soles).
Affected children not only have dry, sensitive skin; their skin is actually thin and fragile as well. Plastic or other synthetic shoe surfaces worn in the summertime are thought to contribute to the friction, heat, and sweating necessary to produce these changes.
As in this case, JPD is often mistaken for tinea pedis but has nothing to do with infection of any kind. Tinea pedis is uncommon in children this young, and it would present in completely different ways, such as between the toes (especially the fourth and fifth) or with blisters on the instep.
Psoriasis, though not unknown in this age-group, does not resemble JPD clinically at all. When suspected, the diagnosis of psoriasis can be corroborated by finding it elsewhere (eg, through a positive family history or biopsy).
Pitted keratolyis is common enough, but is seen in older teens and men whose feet are prone to sweat a great deal. The choice of shoes and occupation are often crucial factors in its development. The clinical hallmark is arcuate whitish maceration on weight-bearing surfaces, which are often malodorous as well.
TREATMENT
The first treatment for JPD is education of parents and patients, reassuring them about the relatively benign nature of the problem. Moisturizing frequently with petrolatum-based moisturizers is necessary for prevention, but changing the type of shoes worn is the most effective step to take; it is also the most difficult, since children this age favor cheap, plastic flip-flops or shoes in the summer.
For the fissures, spraying on a flexible spray bandage can be helpful in protecting them and allowing them to heal. With significant inflammation, the use of mild steroid ointments, such as hydrocortisone 2.5%, can help. But by far, the best relief comes with the change in season and the choice of shoe (leather-soled).