A rare case of compound heterozygous Southeast Asian double α-globin gene deletion and Haemoglobin Quong Sze in a Malay proband

INTRODUCTION: Haemoglobin (Hb) Quong Sze is a non-deletional α-thalassaemia subtype that occurs due to missense mutation at codon 125 of the HBA2 gene. Interaction between Hb QS with Southeast Asian double α-globin gene deletion results in non-deletional HbH disease, which is more severe than deletional HbH.

CASE REPORT: A 3-month-old baby boy was presented with neonatal anaemia and mild hepatomegaly. Full blood count revealed severe hypochromic microcytic anaemia. There was an abundance of HbH inclusion bodies in his red blood cells. High-performance liquid chromatography showed a reduced HbA2 level with the presence of pre-run peak. Capillary electrophoresis showed the presence of HbH and Hb Barts. Molecular analysis found a common α0-thalassaemia (--SEA) in one allele and mutation in codon 125 in the other allele.

DISCUSSION: Non-deletional HbH disease due to a combination of deletional and non-deletional mutations may present with severe clinical manifestations than those with deletion mutations, which warrants accurate diagnosis using molecular techniques.