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Previously misdiagnosed red cell membrane disorder and familial consequences

A 14-year-old girl was referred because of a rapid loss of weight (6 kg within the previous 2 weeks) associated with jaundice and frequent headaches. No aetiology was identified and the diagnosis of an eating disorder was considered. However, some findings suggested well-compensated haemolysis. The reticulocyte count and mean corpuscular haemoglobin concentration (MCHC) were obviously elevated (202 9 10/l and 383 g/l, respectively) without anaemia (haemoglobin concentration 142 g/l), and with increased unconjugated bilirubin (53 μmol/l). Further questioning with regard to family history revealed that several members (mother, grandmother and grandaunt) had previously been diagnosed with hereditary spherocytosis (HS), but the topic was quite taboo within the family, following the loss of the grandmother, who had been splenectomised and had died of pulmonary embolism several months later. Because of the significant family history and laboratory results, the diagnosis of HS in the girl was explored: unexpectedly the eosin-5-maleimide (EMA) binding test was clearly normal and a semi-automated osmotic fragility test (OFT) with Osmocells did not show any increased fragility; rather, red cells were found to have increased resistance to hypotonic conditions. In addition, careful re-examination of a blood film revealed the presence of a small number of stomatocytes associated with a few spherocytes (left). Ektacytometry finally revealed a typical profile of dehydrated hereditary stomatocytosis (DHSt) (right – left shift of yellow outline indicating red cell dehydration). In parallel, her mother was re-investigated and showed superimposable abnormalities with regard to full blood count, erythrocyte morphology (centre), membrane analyses (EMA test, Osmocells and ektacytometry – red outline), confirming the presence of a familial red cell membrane disorder, and a diagnosis of DHSt. Hereditary stomatocytosis is a heterogeneous group of red cells membrane disorders resulting from permeability defects and subsequent changes in erythrocyte hydration. Although the dehydrated form of stomatocytosis (also called hereditary xerocytosis) is considered to be the most frequent form, its precise prevalence is unknown. Furthermore, because of the variety and non-specificity of both clinical symptoms and laboratory data (indicating chronic and well-compensated haemolysis), a number of cases are surely unrecognised, or even misdiagnosed as HS (jaundice, elevated MCHC and reticulocytosis without anaemia being seen in both). A careful review of the blood film is mandatory to guide the diagnosis and the presence of stomatocytes (even in small numbers) should lead to a diagnosis of HS being questioned; the OFT is of interest as it shows increased osmotic resistance, reflecting the dehydrated state of the red cells that allows them to tolerate more hypotonic conditions. The distinction between HS and DHSt is of major importance if splenectomy is being considered, as there is clear evidence that DHSt is associated with an increased risk of postsplenectomy thromboembolic complications. This is unfortunately illustrated in the reported family.