Analysis of hemochromatosis gene mutations in 52 consecutive patients with polycythemia vera

Hereditary hemochromatosis and JAK2-positive polycythemia vera

A 59-year-old man was diagnosed with JAK2-positive polycythemia vera. Subsequently, further laboratory testing revealed elevated ferritin and iron saturation. Genetic testing for HFE gene mutation screen revealed that the patient was positive for heterozygous C282Y mutation. The patient was ultimately diagnosed with both polycythemia vera and hereditary hemochromatosis.

Polycythemia in Patients With Hereditary Hemochromatosis: Real or Myth?

Background

Hereditary hemochromatosis (HH) is an autosomal recessive disorder affecting iron metabolism, resulting in iron accumulation in tissue parenchymal cells. Missense mutations result in homozygosity or heterozygosity for substitutions in the HFE gene, with the most common being C282Y and H63D.

Methods

With an aim to evaluate an association between polycythemia and HH, retrospective chart review was performed for 152 patients with known HFE mutations. Parameters reviewed included individual HFE genotypes, gender distribution, hemoglobin (Hgb) and hematocrit (Hct) levels, median ferritin levels and whether or not phlebotomy was required.

Results

Of 152 patients, 96 (63.2%) were men and 56 (36.8%) were women. Median Hgb and Hct were noted to be higher in men compared to women irrespective of HFE status. Mean age was 60.5 years (range 22 - 93 years). Regarding HFE mutation, 44 (28.9%) patients were C282Y/C282Y, 10 (6.6%) were H63D/H63D and 27 (17.8%) had one copy of each mutation. One patient in the study group was H63D/S65C. Median Hgb and Hct were noted to be 15.5 g/dL and 44.9% respectively in C282Y/C282Y subjects, 16.0 g/dL and 47% in H63D/H63D subjects, 15.8 g/dL and 46% in C282Y/H63D subjects, 16g/dL and 47% in those with single C282Y mutation and 16.6g/dL and 48% in those with single H63D mutation. A total of 67.1% subjects received phlebotomy. A total of 21.7% patients in this cohort were active tobacco users and only 8.6% had an established pulmonary diagnosis, including obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD). Elevated Hgb levels were noted despite absence of an established reason for secondary polycythemia. Anemia was not encountered despite concurrent medical conditions that would usually be associated with anemia, including gastrointestinal bleeding or end-stage renal disease (ESRD).

Conclusions

Elevated Hgb and Hct levels in HH may be secondary to increased iron uptake by erythroid cell precursors in the bone marrow, in setting of increased availability of both transferrin-bound as well as non-transferrin-bound iron (NTBI). Additional studies need to be pursued to explore the association between HFE mutations and secondary polycythemia.

HFE C282Y mutation as a genetic modifier influencing disease susceptibility for chronic myeloproliferative disease

Iron metabolism has been implicated in carcinogenesis and several studies assessed the potential role of genetic variants of proteins involved in iron metabolism (HFE C282Y, TFR S142G) in different malignancies. Few reports addressed this issue with relation to chronic myeloproliferative disorders (CMPD). The aims of our study were (a) to examine the potential associations of CMPD development with genetic modifiers of iron metabolism in a large cohort of CMPD patients; (b) to examine associations of genetic variants of proteins involved in iron metabolism; and acquired JAK2 V617F mutation with clinical characteristics of CMPD. HFE C282Y was genotyped in 328 CMPD patients and 996 blood donors as controls, HFE H63D, and TFR S142G were tested in CMPD patients and 171 first time blood donors. JAK2 V617F mutation was tested in CMPD patients and in 122 repeated blood donors. Decreased C282Y allele frequency (allele frequency+/-95% confidence interval) was found in the CMPD group (1.8%+/-1.0%) compared with controls (3.4%+/-0.8%; P=0.048). TFR S142G allele frequency was reduced among V617F-negative CMPD patients (34.8%+/-7.6%) compared with controls (47.8%+/-5.4%; P=0.02). The frequency of JAK2 V617F was 75.9% (249 of 328) in the CMPD group. At presentation, elevated hemoglobin levels were found in V617F-positive patients compared with V617F-negative counterparts (P<0.000). Vascular complications (26.6% versus 15.2%; P=0.039) as well as female gender (57.4% versus 41.8%; P=0.019) were more common in V617F-positive patients. We found that HFE C282Y might be associated with a protective role against CMPD. Because chronic iron deficiency or latent anemia may trigger disease susceptibility for CMPD, HFE C282Y positivity may be a genetic factor influencing this effect.