Polycythemia in Patients With Hereditary Hemochromatosis: Real or Myth?

Hemochromatosis Gene Mutation in Persons Developing Erythrocytosis on Combined Testosterone and SGLT-2 Inhibitor Therapy

In clinical trials, sodium-glucose cotransporter-2 inhibitors (SGLT-2i) use alone in persons with type 2 diabetes (T2D) or testosterone replacement therapy (TRT) prescription alone in men with hypogonadism was shown to lead to a modest but significant increase in red blood cell mass. Recent evidence indicates that combined use of TRT and SGLT-2i in persons with T2D may be associated with risk of erythrocytosis. However, factor(s) that may lead to the development of erythrocytosis in these patients is unknown. We describe here 5 consecutive patients with hypogonadism on chronic TRT who developed erythrocytosis following addition of SGLT-2i empagliflozin for optimization of T2D management. In addition to the careful review of medical history, all patients underwent genetic screening for hereditary hemochromatosis. We have found that none of the patients had C282Y mutation in the HFE (Homeostatic Iron Regulator) gene and 4 out of 5 patients had heterozygosity in the H63D allele. Upon TRT discontinuation or its dose reduction or referral for scheduled phlebotomy, patients showed resolution of erythrocytosis. Our study reaffirms that practitioners should monitor for changes in hematocrit following the initiation of SGLT-2i in persons with T2D and hypogonadism on chronic TRT. Also, for the first time, we showed that in some of the patients receiving combined TRT and SGLT-2i H63D heterozygosity in the HFE gene may mediate the development of new-onset erythrocytosis.

Identification of Variants Associated With Rare Hematological Disorder Erythrocytosis Using Targeted Next-Generation Sequencing Analysis

An erythrocytosis is present when the red blood cell mass is increased, demonstrated as elevated hemoglobin and hematocrit in the laboratory evaluation. Congenital predispositions for erythrocytosis are rare, with germline variants in several genes involved in oxygen sensing (VHL, EGLN1, and EPAS1), signaling for hematopoietic cell maturation (EPOR and EPO), and oxygen transfer (HBB, HBA1, HBA2, and BPGM) that were already associated with the eight congenital types (ECYT1–8). Screening for variants in known congenital erythrocytosis genes with classical sequencing approach gives a correct diagnosis for only up to one-third of the patients. The genetic background of erythrocytosis is more heterogeneous, and additional genes involved in erythropoiesis and iron metabolism could have a putative effect on the development of erythrocytosis. This study aimed to detect variants in patients with yet unexplained erythrocytosis using the next-generation sequencing (NGS) approach, targeting genes associated with erythrocytosis and increased iron uptake and implementing the diagnostics of congenital erythrocytosis in Slovenia. Selected 25 patients with high hemoglobin, high hematocrit, and no acquired causes were screened for variants in the 39 candidate genes. We identified one pathogenic variant in EPAS1 gene and three novel variants with yet unknown significance in genes EPAS1, JAK2, and SH2B3. Interestingly, a high proportion of patients were heterozygous carriers for two variants in HFE gene, otherwise pathogenic for the condition of iron overload. The association between the HFE variants and the development of erythrocytosis is not clearly understood. With a targeted NGS approach, we determined an actual genetic cause for the erythrocytosis in one patient and contributed to better management of the disease for the patient and his family. The effect of variants of unknown significance on the enhanced production of red blood cells needs to be further explored with functional analysis. This study is of great significance for the improvement of diagnosis of Slovenian patients with unexplained erythrocytosis and future research on the etiology of this rare hematological disorder.

Polycythemia and Anemia in Hereditary Hemochromatosis

Introduction Hereditary hemochromatosis is a syndrome of dysregulated iron homeostasis resulting in the excessive deposition of iron. Hemochromatosis causes pulmonary, pancreatic, and hepatic dysfunction, all of which are risk factors for anemia in the general population. Conversely, iron overload states are thought to predispose to polycythemia. The effect of the homozygosity and heterozygosity of hereditary hemochromatosis-associated genes on hemoglobin levels has not been sufficiently studied. Materials and methods We conducted a retrospective cohort study at West Virginia University of all patients who underwent HFE gene analysis and carried the diagnosis of hemochromatosis. Charts were reviewed to identify relevant variables and the patients' clinical course. Results A total of 213 patients were included with 143 male participants (67.13%). The mean age was 53.6 years (SD: 15.2). A total of 108 patients were homozygous for the C282Y mutation. The prevalence of baseline characteristics are as follows: tobacco use 46.3%, chronic obstructive pulmonary disease 16.4%, malignancy 20.1%, cirrhosis 16.8%, anticoagulant use 6.5%, and chronic renal insufficiency 13.1%. The mean hemoglobin of the population was 15.0 mg/dL (SD 2.21). Anemia was seen in 23 patients (10.80%) and 59 patients (27.6%) had polycythemia. Concurrent malignancy and the presence of chronic renal insufficiency were significantly associated with anemia in both the univariate and multivariate analysis (p-values < 0.001). Patients with homozygosity for C282Y were more likely to receive phlebotomy as compared to other patients. Serum ferritin was not associated with anemia or polycythemia on multivariate analyses (p-values 0.197 and 0.105, respectively). Conclusion Despite the high prevalence of comorbidities that are known risk factors for anemia in the general population, few patients with hereditary hemochromatosis develop anemia. Female patients with hereditary hemochromatosis are relatively protected against polycythemia, affecting only one-fourth of all patients with hemochromatosis, with most patients' serum hemoglobin reported within normal limits.