Familial primary localized cutaneous amyloidosis in Brazil.

BACKGROUND Macular and lichen amyloidosis are clinical variants of primary localized cutaneous amyloidosis (PLCA). Most cases are sporadic, but approximately 10% of cases may be familial. To our knowledge, the clinicopathologic and molecular features of such pedigrees, however, have not been studied in detail. OBSERVATIONS We assessed 2 Brazilian families with either lichen-type (family 1 had 14 affected subjects) or macular-type (family 2 had 7 affected subjects) PLCA. Typically, in both pedigrees, the onset of symptoms was around puberty, and pruritus usually began on the lower legs. Findings from lesional skin biopsy samples from both families showed thioflavin T-positive material in the papillary dermis, which was more prominent in the lichen phenotype in family 1. Spontaneous improvement occurred in 3 subjects (from both families) after age 25 years. All affected individuals in family 1 had a heterozygous missense mutation in the OSMR gene (p.I691T), but no pathogenic mutation in OSMR was found in family 2. CONCLUSIONS Familial PLCA shows autosomal dominant inheritance, but there is clinical and genetic heterogeneity and variable clinical penetrance. Demonstration of mutations in the OSMR gene provides new insight into mechanisms of itch and apoptosis in human skin.