Junctional Epidermolysis Bullosa: A Clinical Overview

Abstract

Junctional epidermolysis bullosa is an autosomal recessive disorder characterized by the formation of blisters at the lamina lucida, an electron-lucent zone located between the basal cell plasma membrane and the lamina densa (Fig. 8.1). Like other forms of epidermolysis bullosa (EB), several subtypes are recognized (Table 8.1). These are differentiated mainly on the basis of clinical manifestations, and it is unclear if they represent varying expressivity of a single defective gene, or diseases caused by abnormalities at different genetic loci. Staining with monoclonal antibodies directed at various basement membrane zone antigens is useful in characterizing certain forms of junctional EB,1 and this is topic is discussed in detail in Chapter 3. Abnormalities of hemidesmosomes have been observed in skin biopsy specimens from patients with junctional EB, especially those with the “letalis” form.2 Reduced numbers of morphologically ill-defined “hemidesmosomelike structures” have been observed in cultured keratinocytes obtained from junctional EB patients.3 In another study, cultured keratinocytes obtained from three patients with a nonletalis type of junctional EB showed altered structural, adhesive, and functional abnormalities.4 Compared with normal keratinocytes, junctional EB cells showed elongated refractile appearance, diminished cell-stratum adhesion, and were slow growing.4 A condition similar to junctional EB has been described in the toy poodle.5