Finally, our study revealed that most of what is considered the extreme phenotype of hemochromatosis—which includes liver cirrhosis, hepatocellular carcinoma, and cardiac phenotypes, specifically cardiomyopathies—does not differ across genotypes, which is consistent with the fact that these late manifestations are nowadays uncommon as a consequence of HH and can be prevented by the early detection and treatment of HH with phlebotomy. The exception to this was diabetes, a late HH complication that we found more frequently among homozygous than among compound-heterozygous males. Furthermore, early signs of hemochromatosis (e.g., fatigue, arthritis, and skin hyperpigmentation) did not significantly differ by genotype, possibly because these signs are difficult to define, might not be captured in the electronic health record, and occur commonly in the population at large and thus limit power.