Objective To evaluate the spectrum of genetic defects in Indian patients with unexplained erythrocytosis. Methods Fifteen families (18 patients) with unexplained erythrocytosis were enrolled after excluding polycythemia vera and secondary erythrocytosis. Focused Sanger sequencing from genomic DNA was performed for EPOR (exon 8), VHL (exons 2‐3), EGLN1 (exons 2‐5), EPAS1 (exon 12), and all exons of HBB, HBA1, and HBA2 genes. Results Eleven of the 18 patients (including two pairs of brothers) had Chuvash polycythemia, that is, homozygosity for VHL:c.598C > T (p.Arg200Trp). Three patients (two of whom were brothers) had HBB mutations associated with increased oxygen‐affinity hemoglobin—one had a heterozygous Hb McKees Rocks HBB:c.438T > A (p.Tyr146*), and two brothers showed heterozygous Hb Rainier HBB:c.437A > G (p.Tyr146Cys). No pathogenic variants were found in the remaining four cases. Conclusion A gene‐by‐gene Sanger sequencing approach could determine a genetic basis for erythrocytosis in 11 of the 15 (73%) Indian families, with homozygous VHL:c.598C > T (p.Arg200Trp) being the commonest pathogenic variant. This first study from the Indian subcontinent provides a rationale for analyzing this variant in patients with suspected congenital erythrocytosis from this region. Rare first occurrences of Hb McKees Rocks and Hb Rainier in Indians are also being reported.

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis seen in association with systemic disorders including hematologic malignancies. Hairy cell leukemia (HCL) however, is an unusual association of PG. We describe a 49-year old lady who presented to our hematology clinic with easy fatiguability and ulcerative skin lesions of 6 months duration. Examination revealed pallor and massive splenomegaly. Indurated, ulcerated lesion with undermined edges and necrotic base was observed on left thigh. Investigations revealed pancytopenia and bone marrow examination identified typical hairy cells. Flow cytometry of marrow aspirate was suggestive of classical HCL. BRAF V600E mutation was detected in peripheral blood by reverse transcriptase polymerase chain reaction. Skin biopsy revealed neutrophilic dermatosis and findings classical of bullous PG. Cladribine therapy (0.09 mg/kg/day by continuous intravenous infusion for 7 days) led to remission of both HCL and PG after a duration of 4 weeks. Cladribine monotherapy in a case of PG with HCL may avoid the additional immunosuppresion risk imposed by treating PG separately with corticosteroids. Immunosuppressive role of cladribine might be helpful in treating PG concurrent with HCL.

Erythrocytosis, or increased red cell mass, may be labeled as primary or secondary, depending on whether the molecular defect is intrinsic to the red blood cells/their precursors or extrinsic to them, the latter being typically associated with elevated erythropoietin (EPO) levels. Inherited/congenital erythrocytosis (CE) of both primary and secondary types is increasingly recognized as the cause in many patients in whom acquired, especially neoplastic causes have been excluded. During the past two decades, the underlying molecular mechanisms of CE are increasingly getting unraveled. Gain‐in‐function mutations in the erythropoietin receptor gene were among the first to be characterized in a disorder termed primary familial and congenital polycythemia. Another set of mutations affect the components of the oxygen‐sensing pathway. Under normoxic conditions, the hypoxia‐inducible factor (HIF), upon hydroxylation by the prolyl‐4‐hydroxylase domain protein 2 (PHD2) enzyme, is degraded by the von Hippel‐Lindau protein. In hypoxic conditions, failure of prolyl hydroxylation leads to stabilization of HIF and activation of the EPO gene. CE has been found to be caused by loss‐of‐function mutations in VHL and PHD2/EGLN1 as well as gain‐of‐function mutations in HIF‐2α (EPAS1), all resulting in constitutive activation of EPO signaling. Apart from these, globin gene mutations leading to formation of high oxygen affinity hemoglobins also cause CE. Rarely, bisphosphoglycerate mutate mutations, affecting the 2,3‐bisphosphoglycerate levels, can increase the oxygen affinity of hemoglobin and cause CE. This narrative review examines the current mutational spectrum of CE and the distinctive pathogenetic mechanisms that give rise to this increasingly recognized condition in various parts of the world.

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Liver transplant recipients are at an increased risk of opportunistic infections due to use of immunosuppression. Coronavirus disease of 2019 (COVID-19) increases the risk of these infections further due to associated immune dysfunction and use of high dose steroids. We present a case of liver transplant recipient who developed disseminated tuberculosis and invasive pulmonary aspergillosis complicated by acquired hemophagocytic lymphohistiocytosis after recovering from severe COVID-19.