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With regard to the mode of inheritance of hemochromatosis, it is of interest, and perhaps significant, that the "minor abnormalities in iron metabolism demonstrable in first degree relatives of probands" have never been demonstrated in both parents of probands. The family studied by Drs. Powell and Lloyd provides an example. On the other hand, florid hemochromatosis is, from time to time, encountered in one or another parent of patients with florid disease. Again, the family studied by Drs. Powell and Lloyd provides an example. If the florid disease does represent homozygosity, its occurrence in successive generations requires the mating of successive pairs of heterozygous carriers of an uncommon gene.
Alternatively, the differences in severity of the abnormalities of iron metabolism may result from differences of expressivity and of environment (eg, alcoholism, iron-loaded diet, or menorrhagia) rather than from heterozygosity vs homozygosity.
Crosby WH. Hemochromatosis-Reply. Arch Intern Med. 1975;135(9):1269. doi:10.1001/archinte.1975.00330090141020