Hemoglobin (Hb) Q-Thailand, also known as G-Taichung, Mahidol, Kurashiki-I and Asabara, is an α-globin chain variant that results from a point mutation (GAC→CAC; Asp→His) at codon 74 of the α1-globin gene on chromosome 16p with a leftward single α-globin gene deletion (-α4.2). Co-inheritance of Hb Q-Thailand with α-thalassemia (mainly --SEA) results in thalassemia intermedia, termed Hb Q-H disease. The aim of the present study was to identify Hb Q-H disease in a Cantonese family. The presence of the Hb variant was confirmed by cellulose acetate electrophoresis. DNA analysis, based on polymerase chain reaction and sequencing, was developed to identify the αQ-Thailand mutation and common α-thalassemia gene deletions. Three cases of Hb Q-H disease and two Hb Q-Thailand carriers were found in the family. The 3-day-old proband with Hb Q-H disease did not show anemia (Hb 144g/l), having 25.47% Hb FQ (αQ2γ2) in the total Hb; the other two cases of Hb Q-H disease manifested mild-to-moderate anemia. None required regular transfusions.

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