Mitten deformity in severe generalized recessive dystrophic epidermolysis bullosa: histological, immunofluorescence, and ultrastructural study.

Light and electron microscopy and indirect immunofluorescence techniques were used to study the nature of the mitten deformity in five adult patients with severe generalized recessive dystrophic epidermolysis bullosa undergoing release of hand and finger contractures. Although the mitten appeared largely to be clinically separated from the underlying fixed digits, histology showed mostly normal keratinocytes beneath a thickened stratum corneum. The lower margin of the mitten was formed just below the lamina densa of the basement membrane, at a level similar to that of the usual blister formation in this condition. No anchoring fibrils and only a few distinct dermal structures were noted. A substantial portion of the mitten, however, consisted of necrotic keratinocytes without an intact basement membrane. This finding suggests that the mitten is not suitable for use as an epidermal autograft and confirms the rationale for taking split thickness skin grafts to close skin defects in patients with recessive dystrophic epidermolysis bullosa undergoing plastic surgery.