Association between heterozygous β₁-antitrypsin deficiency and genetic hemochromatosis

Primary hemochromatosis is a genetically determined autosomal recessive disorder characterized by the excessive accumulation of body iron, most of which is deposited in the parenchymal cells of various organs.

β₁-Antitrypsin deficiency is characterized among others by defective secretion of β₁-antitrypsin from liver cells. Whereas the risk of cirrhosis is increased in homozygous patients (P1 ZZ) and possible in heterozygous patients (non-PI MM) as well, a greater risk for hepatocellular carcinoma has been suggested only in homozygous patients.

Because these two metabolic disorders are relatively common, it has been difficult to determine whether they are associated with each other. In this study, we tried to determine the relationship between these two disorders using the case material seen at the University of Pittsburgh during a 7-yr period.

We studied 15 patients with genetic hemochromatosis. β₁-Antitrypsin quantitation and phenotyping were performed in each case using standard methods. The distribution of the various Pi phenotypes was compared with that found in a normal population and reported elsewhere. Odds ratio and χs² tests were used to measure the relative risk and significance of association, respectively.

Eleven patients (73%) were found to be PI M and four (27%) were identified as being heterozygotes: three (20%) were PI MZ, and one (7%) was PI MS. The prevalence of the PI MS phenotype was similar to that in the general population (7% vs. 6.4%; NS). The PI MZ phenotype, however, was statistically more common in patients with hemochromatosis than in the general population (20% vs. 2.2%; p <0.004). The odds of having hemochromatosis among PI MZ patients is increased 11-fold (odds ratio = 11.25; 95% confidence interval: 1.95, 44.23). The mean serum level of β₁ antitrypsin and the occurrence of hepatocellular carcinoma was similar in the patients with the PI M and non-PI M phenotypes.

It can be concluded that abnormal β₁-antitrypsin alleles are seen more frequently in patients with genetic hemochromatosis than in the general population. Their coexistence may contribute to the earlier development of cirrhosis in some of these patients. However, it does not increase the risk for hepatocellular carcinoma despite the fact that each disorder alone is known to do so. (HEPATOLOGY 1992;16:145–148.)