Derma sce dr .lana

9. Inherited dyschromatoses Dyschromatoses are disorders characterized by both hyperpigmented and hypopigmented macules. A. Dyschromatosis symmetrica hereditaria (DSH) Also known as reticulate acropigmentation of Dohi. Characterized by hyperpigmented and hypopigmented macules, classically in a symmetrical acral distribution. The chapter describes increased melanin in basal keratinocytes in hyperpigmented macules and reduced density of DOPA-positive melanocytes in hypopigmented macules. Mutations in the RNA-specific adenosine deaminase gene (ADAR, historically DSRAD) are associated with the condition. Treatment is unsatisfactory; strict sun avoidance may reduce the contrast between lesions. B. Dyschromatosis universalis hereditaria (DUH) Rare disorder with generalized hypo- and hyperpigmented macules. Usually begins in early childhood. Most reported patients in the chapter are Japanese, although cases have been reported in other populations. Autosomal dominant forms are associated with mutations in ABCB6; SASH1 mutations can also cause DUH. Histology shows focal increases or decreases in melanin in the basal epidermis in hyperpigmented and hypopigmented areas, respectively. Treatment: No satisfactory treatment is available. C. Important differential diagnosis Xeroderma pigmentosum: May produce hyper- and hypopigmented macules in childhood, but the lesions show a photodistribution and are associated with premature actinic damage. DSH: Predominantly acral and symmetrical. DUH: More generalized distribution, usually with early-childhood onset. Final exam trap: Both DSH and DUH feature hyperpigmented and hypopigmented macules, but DSH is predominantly acral and symmetrical, whereas DUH is generalized.