An unexpectedly bizarre blood film in hemoglobin H disease

Abstract

A 3-year-old boy from Saudi Arabia had been followed up with a diagnosis of hemoglobin H disease, identified in a neonatal screening programme. His parents were second cousins. Alpha globin genotyping at birth had revealed homozygosity for the non-deletional Saudi-T mutation (αTα/αTα), both parents being carriers. He had remained clinically asymptomatic. Red cell indices at the age of three years were: RBC 3.84 x 1012/l, hemoglobin concentration 80 g/l, MCV 61 fl, MCH 20.9 pg, MCHC 34 g/l, red cell distribution width 34.8 (normal range 11.8-14.3) and reticulocyte count 447 x109/l. His blood film, in addition to microcytosis, showed gross poikilocytosis with the abnormal red cells including elliptocytes and many bizarre poikilocytes, some very small (image). Although poikilocytosis can be prominent in hemoglobin H disease, we have not seen a case with this degree of abnormality. The film was reminiscent of hereditary pyropoikilocytosis. For this reason red cell membrane studies were initiated. An eosin-5 maleimide (EMA)-binding assay [1] gave a twin peak fluorescence profile: 57% of phenotypically normal red cells (MCF = 64.7 units) and 42% having reduced fluorescence (MCF = 32.4 units). Spectrin (Sp) analysis showed a Sp dimer content of 25.6 %, compared with 7.4 % for a normal control within the same assay. In limited trypsin digestion of spectrin, SpαI/50 variant was detected in the child, and absent in the mother. Neither had an increase of SpαV/41 tryptic peptide, thus excluding the presence of the polymorphic low expression allele, SpαLELY. Maternal red cells were not elliptocytic and had normal spectrin dimer content and normal EMA binding. A paternal sample was not available for testing. Although the EMA-binding assay has high specificity and sensitivity for hereditary spherocytosis, it can also be abnormal in hereditary pyropoikilocytosis, Southeast Asian ovalocytosis, cryohydrocytosis, and some cases of congenital dyserythropoietic anemia type II [2]. Hereditary elliptocytosis usually gives a single fluorescence peak within the range for normal red cells but occasionally twin peaks are observed. In this child with co-inheritance of hemoglobin H disease and hereditary elliptocytosis, the severity of the hemolytic anaemia is that expected in uncomplicated hemoglobin H disease but the bizarre blood film reflects an interaction of the hemoglobinopathy and the membrane defect. 1