Genetic and Clinical Features of Hemoglobin H Disease in Chinese Patients
Frederick E. Chen, M.D., Clara Ooi, M.B., B.Ch., Sau Yin Ha, M.B., B.S., Bernard M.Y. Cheung, M.B., B.Chir., David Todd, M.D., Raymond Liang, M.D., Tai Kwong Chan, M.D., and Vivian Chan, Ph.D.
Background Normally, one pair of each of the two -globin genes,1 and 2, resides on each copy of chromosome 16. In hemoglobinH disease, three of these four -globin genes are affected bya deletion, a mutation, or both. We studied the -globin geneabnormalities and the clinical and hematologic features of Chinesepatients with hemoglobin H disease in Hong Kong.
Methods We assessed the clinical features, hematologic values,serum ferritin levels, and liver function of 114 patients withhemoglobin H disease. We also performed echocardiography andmagnetic resonance imaging of the liver and examined the twopairs of -globin genes.
Results Hemoglobin H disease in 87 of the 114 patients (76 percent)was due to the deletion of three of the four -globin genes (/),a combination termed the deletional type of hemoglobin H. Theremaining 27 patients (24 percent) had the nondeletional typeof hemoglobin H disease, in which two -globin genes are deletedand a third is mutated (/T). All 87 patients withthe deletional type of hemoglobin H were double heterozygotesin whom there was a deletion of both -globin genes from onechromosome, plus a deletion of the 1 or 2 gene from the otherchromosome (/ or /).A variety of mutated -globin genes was found in the patientswith nondeletional type of hemoglobin H disease. Patients withthe nondeletional type of the H disease had more symptoms ata younger age, more severe hemolytic anemia, and larger spleensand were more likely to require transfusions than patients withdeletional hemoglobin H disease. The severity of iron overloadwas not related to the genotype.
Conclusions Chinese patients in Hong Kong with the nondeletionaltype of hemoglobin H disease have more severe disease than thosewith the deletional type of the disease. Iron overload is amajor cause of disability in both forms of the disease.
Source Information
From the Departments of Medicine (F.E.C., B.M.Y.C., D.T., R.L., T.K.C., V.C.), Radiology (C.O.), and Paediatrics (S.Y.H.), University of Hong Kong and Queen Mary Hospital, Hong Kong, China.
Address reprint requests to Dr. Vivian Chan at the University Department of Medicine, Queen Mary Hospital, Pokfulam Rd., Hong Kong, China, or at vnychana{at}hkucc.hku.hk.
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