Epidermolytic acanthomas: clinical characteristics and immunohistochemical features.

Epidermolytic hyperkeratosis in bullous congenital ichthyosiform erythroderma results from mutations in the K1 and K10 genes. Epidermolytic acanthomas are solitary or multiple lesions with microscopic features that are identical to those in bullous congenital ichthyosiform erythroderma. In this study, the clinical and epidemiologic characteristics of epidermolytic acanthomas were summarized, and the expression of keratins (using antibodies to K1, K6, K10, K14, K16, and K19) in five solitary epidermolytic acanthomas was determined using immunohistochemistry techniques. The intensity of staining for K1 and K10 was (a) less in the altered granular layer, as compared to the adjacent nonaltered granular layer of the lesional skin, and (b) less in the lesional skin as compared to the perilesional, histologically normal-appearing skin. Expression of K6 and K16 was noted not only in the basal layer and suprabasal layers of the lesions, but also in the corresponding layers of the adjacent normal skin. Staining for K14 was also observed in the basal layers and suprabasal layers of the lesional and adjacent normal epidermis; within the lesional and perilesional normal skin, the intensity of positive staining for K14 was greater in the basal layers than in the suprabasal layers of the epidermis. The specimens did not stain for K19. In conclusion, using immunohistochemistry techniques on solitary epidermolytic acanthomas, we were able to demonstrate (1) an abnormality in K1 and K10 expression in the lesional skin as compared to the adjacent, histologically normal-appearing skin and (b) the expression of hyperproliferative keratins not only with the lesional skin, but also in the perilesional normal skin. We hypothesize that the pathogenesis of epidermolytic hyperkeratosis in lesions of solitary epidermolytic acanthomas results from mutations in the K1 and K10 genes.