Differential diagnosis of unusual skin diseases in infants.

There are a number of relatively unique clinical skin diseases that may develop on the buttocks of infants. These include iatrogenic skin diseases caused by external medicine; skin tumors caused by methylrosaniline chloride (Pyoktanin); atrophy of the skin due to steroidal liniments; nevus and tumor diseases, such as nevoxanthoendothelioma and Letterer-Siwe disease. Finally, there is chronic granulomatous disease. These unusual cases are reviewed and their differential diagnoses discussed.