A 15-days old male baby from Cape Town was admitted with rebounding neonatal jaundice and suspected ABO incompatibility. The patient’s parents were both South Africans of mixed ancestry (Cape Coloured). This was their first child with no prior pregnancies. There was no family history of hematological disease. The patient had a mild anemia with hemoglobin, 13.6 g/dL (normal range 14.9 - 22.9), leucocytes and platelets were normal.  The patient had an unconjugated bilirubinemia, with total bilirubin, 260 µmol/L (normal range 5 - 21 ) and conjugated bilirubin 15 µmol/L (normal range 0-20). Lactate dehydrogenase was 416 U/L (180 – 430). Coombs’ test was negative. The peripheral blood film showed macro-ovalocytes and stomatocytes some of which had off center, transverse or less frequently, longitudinal slits. Several red cells have more than one stoma. Some of the stoma were Y-shaped, V-shaped or parallel to each other with two or less frequently, three pale regions separated by a well hemoglobinized ridge, giving the appearance of double stomatocytes or knizocytes. A diagnosis of South-East Asian Ovalocytosis was made. The jaundice subsequently subsided and total bilirubin levels normalised after standard treatment. The baby was then discharged with a follow-up appointment. South-East Asian ovalocytosis (SEAO) can be diagnosed with a high degree of reliability by light microscopic examination of a blood film. The presence of macro-ovalocytes, stomatocytes, and knizocytes should raise the suspicion of SEAO.  The presence of knizocytes alone is a strong predictor of SEAO status irrespective of ovalocyte levels or any other additional morphologic features.1 South-East Asian ovalocytosis heterozygosity is significant only in the neonatal period, when it is associated with clinically significant hemolysis and anemia.2 However, symptomatic heterozygous SEAO has been reported previously in the Cape Coloured population.3

References:

1.        Nixon, C. P. et al. Accurate light microscopic diagnosis of South-East Asian ovalocytosis. Int. J. Lab. Hematol. 40, 655–662 (2019).

2.        Garnett, C. & Bain, B. J. South-East Asian ovalocytosis. Am. J. Hematol. 88, 328 (2013).

3.        Coetzer, T. et al. Southeast Asian ovalocytosis in a South African kindred with hemolytic anemia. Blood 87, 1656–1657 (1996).