A five-generation white family with multiple endocrine neoplasia type 2A had six affected members. Two, a mother and her daughter, had interscapular cutaneous pruritic lesions resembling macular/lichen amyloidosis. In the daughter, light microscopy showed homogeneous aggregates in the papillary dermis. Crystal violet staining showed metachromasia and indicated that the deposits were amyloid. This is the fourth family with familial medullary thyroid carcinoma with cutaneous amyloidosis and as such it allowed comparative analysis. Genetic heterogeneity, a contiguous gene, and pleiotropy were considered. It appears that multiple endocrine neoplasia type 2A/familial medullary thyroid carcinoma with cutaneous amyloidosis represents the phenotypic variability of the expression of a pleiotropic gene. The condition is one of the predominantly ectodermal autosomal dominant phakomatoses and is most likely a paracrinopathy.