[Keratosis palmoplantaris diffuse circumscripta (Thost-Unna) with micropenis]

We report on a 2-year-old boy showing diffuse palmoplantar keratoderma (Thost-Unna's disease) in association with congenital penis hypoplasia. Family history research proved palmoplantar keratoderma autosomally dominant over 5 generations. The boy's 6-month-old brother also shows penis hypoplasia, as yet, however, without signs of palmoplantar keratoderma. So far we are not able to settle the question whether this case represents a clinical entity of its own or merely a chance association of rare symptoms.