Adenoma sebaceum is a germ plasm developmental defect of the skin, involving especially the sebaceous glands. Other elements of the skin, however, may be affected, as noted by Balzer,1 Crocker,2 and others, and confirmed by a study of the case herein reported. In the Balzer type of adenoma sebaceum, changes in the sebaceous glands may be slight. The Pringle type is characterized by an enormous hyperplasia of the sebaceous glands. The Hallopeau-Leredde type shows a predominance of the fibroma element; the surface may be verrucose. Mixed types, in which one lesion shows great hyperplasia of the sebaceous glands and a neighboring lesion may show only nonsebaceous changes, are not uncommon.
The germ plasm defect affects not only the skin, but also a number of other organs: the brain, kidney, heart, intestine and liver, and probably other organs. The changes in these organs are analogous to those in the