Genetic Diseases

Abstract

Many dermatologic diseases have a genetic component, and so this group of diseases may be expanded as more evidence is unearthed. Atopic dermatitis, for instance, is currently included in the dermatitis/eczema group. Filaggrin gene defects have been found in approximately 50% of the patients with atopic dermatitis, but the relationship of this defect to the pathogenesis of this disease has yet to be explained. Psoriasis also likely has a genetic background, but the story is not as well advanced as in atopic dermatitis.

Fabry disease, with the cutaneous finding of angiokeratomas, has the keyword “Maltese cross,” referring to the peculiar pattern seen in the urine under fluorescence microscopy. The angiokeratomas, although very descriptive, may be found in other disorders such as Klippel–Trenaunay–Weber syndrome and are found routinely on the scrotum of elderly men (Fordyce type). ­Angiokeratomas of Mibelli are solitary lesions found most commonly on the extremities. Fabry disease generally is recognized when the angiokeratoma clusters are seen on the abdomen, buttocks, or legs; they are part of a systemic disease with manifestations in other organs such as the kidneys, liver, or heart. Thus, they are an important marker for this systemic disease that results from an accumulation of ceramides in the affected organs. The genetic defect in α-galactosidase results in this accumulation.