Histopathologic and ultrastructural findings in certain genodermatoses

Skin histology and ultrastructure have become diagnostically crucial in relatively few genetic diseases with major or prominent skin manifestations. In some diseases, these morphologic evaluations have increased our understanding of the disease process and provided a basis for interpretation of biochemical and physiologic studies. This review aims at illustrating some of the prominent accomplishments of histologic and, especially, ultrastructural studies in selected genetic diseases. The most widely studied disease group is the epidermolysis bullosa group in which histology and ultrastructure have provided the basis for currently used classifications of the diseases within the group.^1,2 The histologic and ultrastructural findings have also suggested hypotheses concerning the nature of the primary defects in several of these diseases, thus focusing investigations at the physiologic and/or biochemical level. The ichthyoses have been a disappointment from a histologic and ultrastructural point of view, with the exception of epidermolytic hyperkeratosis, in which striking alterations have been noted, although they have yet to lead to a clearer understanding of the nature of the primary defect in the disease.