Interaction of the alpha2 polyadenylation signal mutation (AATAAA-->AATA--) and alpha0-thalassemia (--SEA), resulting in Hb H disease in a Thai patient.

We report a Thai boy with a compound heterozygosity for the alpha2 polyadenylation signal mutation (AATAAA-->AATA--) and alpha0-thalassemia (--SEA), who suffered from Hb H disease with more severe clinical symptoms than those usually observed with deletional Hb H disease. His Hb H level was as high as 52% of total hemoglobin. The hematologic data of this unusual case of Hb H disease was compared with those of Hb H disease with a homozygosity for the alpha2 polyadenylation signal mutation, and compound heterozygosity of the alpha2 polyadenylation signal mutation and alpha0-thalassemia. A simple DNA assay based on an allele specific polymerase chain reaction for the detection of this polyadenylation signal mutation is described.