Epidermolytic hereditary palmoplantar keratoderma. Histologic, ultrastructural, protein-chemical, and DNA analyses in two patients.

Two cases of epidermolytic hereditary palmoplantar keratoderma were studied by histologic, ultrastructural, protein-chemical, and genetic methods. Histologically, epidermolytic hyperkeratosis was seen at the spinous and granular layers. Electron microscopy showed the aggregation of tonofibrils and an early appearance of keratohyaline granules as well as vacuolar formation in the epidermal cells. Some of these morphologic abnormalities were detected even in the basal cells. The decrease of 67-kilodalton (kd) keratin and the appearance of 48-kd keratin were noted by using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Genetic analysis of the keratin gene family using 67-kd keratin complementary DNA by Southern blot analysis revealed the conserved gene organization of the 67-kd keratin gene. These findings suggest that undetermined regulatory abnormalities of keratinization, but not the gene structure itself, may be causative factors of this rare disease.