LAUSR

Dear Editor, The paradoxical combination of absolute erythrocytosis with hemolysis can occur with few high-affinity hemoglobin variants and rarely with polycythemia vera (PV) [1, 2]. Familial (Chuvash) erythrocytosis-2 (OMIM #263400), a rare autosomal recessive disorder due to VHL: c.598C>T (p.Arg200Trp), is not associated with hemolysis [3]. Stomatocytosis is an acquired, artifactual, or rarely inherited finding wherein erythrocytes display a slit-like central pallor; inherited stomatocytosis causes hemolytic anemia/compensated hemolysis with jaundice [4]. We report an intriguing case of Chuvash polycythemia, transient stomatocytosis with compensated hemolysis where targeted next-generation sequencing (NGS) revealed unusual genotypes. A 32-year-old male with familial erythrocytosis (highest recorded hemoglobin 242 g/L, underwent four phlebotomies until date) was found to have massive splenomegaly (19.2 cm span), unconjugated hyperbilirubinemia, and bilateral grade III clubbing. History revealed that he was incidentally diagnosed to have erythrocytosis at the age of 15 years. He had three hospital admissions and had generalized erythema. He also had episodes of jaundice suggestive of hemolysis and one episode of hematemesis. He was the sixth-born among eight siblings; three older siblings had died young, and familial erythrocytosiswas noted for the eldest sibling (died at 40 years). One of the siblings had a history of toe infarction which required amputation. Sanger sequencing for targeted regions implicated with familial erythrocytosis [5] revealed that the patient was homozygous for the genetic variant leading to Chuvash polycythemia NM_000551.3(VHL): c.598C>T (p.Arg200Trp) and his parents were heterozygotes. Splenoportal axis Doppler ultrasound revealed non-cirrhotic portal fibrosis. Blood counts revealed hemoglobin 188 g/L, hematocrit 65.1%, red blood cell count 6.95 × 10/L, MCV 93.7 fl, MCH 27 pg, MCHC 28.8 g%, and RDW-CV 22.9% with normal platelet and leukocyte counts. Serial peripheral smear evaluation reveals stomatocytosis (Fig. 1a) with reticulocytosis (6.0%) (Fig. 1b). Tests for common causes of hemolytic anemia including the methemoglobin reduction test for G6PD deficiency screening were negative. Because of apparent compensated hemolysis with stomatocytosis, targeted NGS using a customized multi-gene panel was performed. Data analysis confirmed homozygous VHL: c.598C > T (p.Arg200Trp). Potentially pathogenic variant/s were absent in the coding or upstream sequences of genes implicated with hereditary stomatocytosis (RHAG, SLC4A1, PIEZO1, KCNN4, SLC2A1, ABCB6, ABCG5, ABCG8, STOM, RHCE). However, a WHO class III hemizygous G6PD Kerala-Kalyan [NM_000402.3 (G6PD): c.1039G>A, (p.Glu347Lys), rs137852339] [6] was found after NGS. Sanger sequencing validated the variant in the index case (Fig. 1c). His mother was heterozygous (Fig. 1d), and his father was normal for G6PD Kerala-Kalyan. The methemoglobin reduction test for G6PD deficiency was repeated andwas again negative. The G6PDKerala-Kalyan is a relatively common WHO class III variant across India, and the enzyme activity is anticipated to be between 10 and 60% of the normal. It is possible that our patient lay on the higher end of the enzyme activity spectrum, and was missed by the methemoglobin reduction test, which is a qualitative test and can be unreliable for enzyme activities higher than 40%. * Reena Das [email protected]; [email protected]