Although most reports of lymphocyte numbers and subsets have been made in persons presumed or documented to have HLA- or HFE-associated hemochromatosis or iron overload, lymphopenia also occurred in an unusual case of early age-of-onset hemochromatosis and severe iron overload associated with homozygosity for a hepcidin promoter mutation on Ch19q13 [33]. Here, HAMP is linked to hemochromatosis type 1.