Clinical features and molecular analysis in Thai patients with HbH disease

We studied the α-globin gene abnormalities, the clinical features, hematologic values, growth assessment, transfusion therapy, and serum ferritin levels of patients with hemoglobin H (HbH) disease in southern Thailand. HbH disease in 83 of the 147 patients was the deletional type of HbH. The remaining 64 patients was the nondeletional type of HbH disease. All 83 patients with the deletional type were double heterozygotes of α⁰-thalassemia and α⁺-thalassemia. The Southeast Asian type of α⁰-thalassemia accounted for 98% of the Thai patients with HbH disease and the Thai type of α⁰-thalassemia made up the rest. A 3.7-kb deletion accounted for 91% of α⁺-thalassemia, and a 4.2-kb deletion made up the rest of the deletional type. In patients with nondeletional type of HbH disease, the Constant Spring variant was the majority of the disease. Newborns with a nondeletional genotype had higher mean corpuscular volume, had higher mean corpuscular hemoglobin, had higher red blood cell distribution width, had lower mean corpuscular hemoglobin concentration, and had higher proportions of Hb Bart's than those with a deletional genotype. Twenty-one percent of children with HbH disease had growth deficiency. A genotype–phenotype correlation was found; patients with the nondeletional type of HbH disease had more symptoms at a younger age, more severe hemolytic anemia, more growth deficiency, more dysmorphic facial features, larger spleens, larger livers, and higher serum ferritin levels and required more transfusions than patients with deletional HbH disease.