Recessive dystrophic epidermolysis bullosa skin displays a chronic growth-activated immunophenotype. Implications for carcinogenesis.

Epidermolysis bullosa represents a grouping of inherited skin diseases characterized by epidermal fragility and frequently wounded skin. The recessive dystrophic subtype of epidermolysis bullosa (RDEB) is characterized by extensive dermal scarring after healing of repeated epidermal injuries and by an unusually high incidence of squamous cell carcinoma occurring in chronically wounded skin. In contrast, the simplex form of epidermolysis bullosa usually heals without scarring and does not predispose to malignant neoplasms of the skin. The differences in scarring and the neoplastic potential of these two forms of epidermolysis bullosa prompted us to investigate growth activation and differentiation characteristics in epidermal keratinocytes in individuals with these disorders. The expression of filaggrin, involucrin, cytokeratins, and the growth activation marker psi-3 was examined by immunohistochemistry in skin biopsy specimens from four individuals with epidermolysis bullosa simplex and six individuals with RDEB. Previous experiments using this technique have demonstrated that these antibodies are good markers for identifying growth-activated keratinocytes in wounded and hyperplastic epidermis. All biopsy specimens of healed wounds in skin from patients with RDEB showed epidermis that reacted with antibodies to filaggrin, involucrin, specific cytokeratins, and psi-3 in a growth-activated pattern. This growth-activated phenotype was maintained in keratinocytes from previously wounded skin that had been healed for more than 2 years. The RDEB growth-activated phenotype detected by immunohistochemistry was not associated with microscopically detectable epidermal hyperplasia. In contrast, all cases of epidermolysis bullosa simplex examined showed an epidermal phenotype similar to that of keratinocytes in normal skin. Thus, healing with dermal scar formation in RDEB is associated with a persistent growth-activated immunophenotype of epidermal keratinocytes. This chronic growth activation state or failure of cells to differentiate in a normal fashion may be directly linked to the high incidence of squamous cell cancers in individuals with RDEB.