GSTM1 and glycogen storage disease VI: Among patients with deletional Hb H disease, the rightward deletion of 3.7 kb (-α3.7) was the most common type of mutation (71.2%), followed by the leftward deletion of 4.2 kb (-α4.2) and the G-Taichung variant with the 4.2 kb deletion (-α4.2  G-Taichung).