Normal ferroportin protein must form multimers (shown here as dimers) to localize properly to the cell surface for cellular iron export. Ferroportin protein carrying the H32R mutation does not traffic to the cell surface. Multimers containing both normal ferroportin polypeptide and mutant ferroportin polypeptide are similarly retained within the cell. Thus, a missense mutation in one allele results in substantial loss of ferroportin activity and clinical disease.