Pathogenic mechanisms in epidermolysis bullosa naevi

Epidermolysis bullosa naevi are large, eruptive melanocytic naevi which frequently arise in areas of former blisters in patients suffering from inherited epidermolysis bullosa. Morphologically, these naevi are similar to malignant melanoma, although so far no malignant transformation has been observed. To investigate the pathogenesis of these moles we documented their clinical evolution and their histopathological and immunocytological characteristics in three patients with epidermolysis bullosa. Clinically, we observed signs of malignant transformation, such as explosive growth and the occurrence of satellite lesions of epidermolysis bullosa naevi. However, malignant melanoma was excluded by histopathological evaluation. In addition, we evaluated the concentrations of various factors known to stimulate melanocyte growth in blister fluid. Human interleukin 8, basic fibroblast growth factor, human hepatocyte growth factor, GM-CSF, leukotriene B4 and prostaglandin E2 revealed concentrations comparable with the levels in inflammatory blisters. We were able to detect individual melanocytes/naevus cells in blister fluid from a blister over an epidermolysis bullosa naevus. The factors detected in the blister fluid might therefore promote the proliferation, migration and melanogenesis of disconnected melanocytes/naevus cells representing the basis of the highly dynamic appearance of epidermolysis bullosa naevi.