OBJECTIVE To describe and characterize the association of hereditary cutaneous lichen amyloidosis with multiple endocrine neoplasia type 2a (MEN 2a). METHODS Survey of a family for two diseases. METHODS Evaluation of patients at a clinical research center. METHODS Nineteen family members with MEN 2a. RESULTS In this family cutaneous lichen amyloidosis presented as multiple infiltrated papules overlying a well-demarcated plaque in the scapular area of the back (right or left). Immunohistochemical studies showed amyloid that stained for keratin but not calcitonin. Three family members had the characteristic skin lesion and also carried the gene for MEN 2a; two additional members carried the gene for MEN 2a, but did not manifest the observable skin changes associated with lichen amyloidosis. CONCLUSIONS From the findings in this kindred and in another recently reported but unrelated family with an identical type of pruritic skin rash and MEN 2a, several conclusions can be drawn. First, the syndrome of cutaneous amyloidosis and MEN 2a is a clearly defined autosomal dominant hereditary syndrome. Second, the dermal amyloid appears to be caused by deposition of keratin-like peptides rather than by calcitonin-like peptides. Third, known families with hereditary lichen amyloidosis should be screened to determine the true frequency of this syndrome.