By Gary M. White, MD
Unna–Thost disease is characterized by a uniformly thick keratoderma covering the palms and soles without involvement of the dorsal hands or feet.
- This autosomal dominant disease usually begins in the first six months of life.
- Hyperhidrosis of the palms and soles, atopic dermatitis, mental retardation, acro-osteolysis, clubbing, and clinodactyly have been associated.
- Based upon genetic studies, the palmoplantar keratoderma (PPK) of both Unna-Thost and Vörner represent the same disease with a causal mutation of the keratin 9 gene on chromosome 17q21 [Arch Dermatol Res 2002;294:268–72].
Both palms and soles are diffusely hyperkeratotic. Often, there is an erythematous rim of demarcation on the lateral palms and soles.
Epidermolytic PPK can present similarly to Unna-Thost disease. Differentiation can be made histopathologically, with the finding of epidermolysis in epidermolytic PPK (see epidermolytic hyperkeratosis).
The patient may be treated with various keratolytic agents topically. 40% urea cream (OTC) is excellent but may irritate normal skin. Oral retinoids, e.g. acitretin 25 mg/day, will usually thin the condition, but bothersome side effects may limit its use.
BMJ Case Reports 2012; doi:10.1136/bcr-2012-006443
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