TUBEROUS SCLEROSIS AND GUTTATE LEUKODERMAS

The clinical, histopathologic, and electron microscopic features of gu ttate leukodermas are reviewed, including the hypomelanoses of the ski n and hair observed in the tuberous sclerosis complex (TSC), The hypop igmentation seen in patients with TSC is related primarily to a decrea se in the function of epidermal and follicular melanocytes; the densit y of active melanocytes is normal, Poorly developed dendritic processe s are observed frequently as are melanosomes that are smaller in size and less melanized than those in melanocytes of uninvolved skin and ha ir, There is also a decreased number of melanosomes within the melanoc ytes, but in the absence of abnormal autophagic aggregation, These hyp ofunctioning melanocytes transfer fewer melanosomes to surrounding ker atinocytes, and therefore the overall melanin content in the affected skin and hair is decreased, Two loci for TSC have been clearly identif ied, and one gene on chromosome 16p13.3 (TSC-2) hers been cloned. The protein product of the TSC2 gene, tuberin, is involved in the regulati on of cellular growth, The second gene is on chromosome 9q34 (TSC-1) n ear the locus for dopamine-o-hydroxylase, an enzyme involved in the sy nthesis of catecholamine neurotransmitters, The differential diagnosis of the guttate leukoderma of TSC includes several clinical entities s uch as idiopathic guttate hypomelanosis, disseminated hypopigmented ke ratoses, and dyschromic amyloidosis. Copyright (C) 1997 by W.B. Saunde rs Company.