Hemojuvelin Mutations in Whites, Blacks and Asians with Primary Iron Overload and in Control Subjects.

Mutations in the hemojuvelin gene (HJV) are a cause of juvenile hemochromatosis (JH), but do they influence the phenotype of patients with adult-onset hemochromatosis with or without mutations of the HFE gene? We sequenced the coding region of the HJV gene of 133 subjects with primary iron overload (75 whites: 50 HFE, 25 non-HFE associated; 51 blacks: 1 HFE-associated; 7 Asians). A 63 year old white woman with non-HFE iron overload was found to be a compound heterozygote for HJV mutations: one previously identified (G320V); the other novel (C321W). The patient was diagnosed at age 30 (SI 223 μg/100 mL, TIBC 293 μg/100 mL, TS 76%, hepatic iron 31,154 μg/g, hepatic iron index 19.2). She had 2 healthy children, developed amenorrhea at age 23, had a history of hypothyroidism and developed Type 2 diabetes at age 59. She was iron depleted after 66 phlebotomies. Among 74 other white subjects with iron overload we found 3 polymorphisms: IVS2-6 C>G (3 subjects); nt 165 T>A (G55G), and IVS4-50 C>T (1 subject, each). Among 51 black iron overloaded and 132 black control subjects, the most notable polymorphism was a DNA triplet insert predicting an insertion of glycine. This was found in 2 subjects, one with and one without iron storage disease. Among the iron overloaded black subjects, we also found IVS2-6 C>G (1 subject), nt -140 G>C (3 subjects), nt 792 G>C (S264S) (1 subject), nt 828 C>A (I275I) (1 subject), and nt 929 C>G (A310G) (2 subjects). These polymorphisms, excluding S264S and I275I, were found in control subjects as well. No coding region mutations or polymorphisms were found in the 7 Asian iron overloaded subjects. We also determined the gene frequency of the HJV I222N and G320V mutations in adult control subjects from central Alabama, where a JH index case had been found with these mutations. Allele frequencies of I222N and G320V were 0.002 (n=240) and 0 (n=241) respectively in control whites. A white control female heterozygous for the I222N was also heterozygous for HFE C282Y but had normal iron measures. No I222N and G320V mutations were found in 124 and 118 black subjects respectively. We conclude that: 1) iron overloaded patients without HFE mutations, with or without a JH phenotype should be screened for HJV; 2) HJV mutations do not account for most cases of increased penetrance of HFE-associated hemochromatosis; 3) double heterozygosity for HFE C282Y and HJV I222N does not necessarily cause iron overload.