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Original Article
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Volume 343:544-550 August 24, 2000 Number 8
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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.

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ABSTRACT

Background Normally, one pair of each of the two {alpha}-globin genes, {alpha}1 and {alpha}2, resides on each copy of chromosome 16. In hemoglobin H disease, three of these four {alpha}-globin genes are affected by a deletion, a mutation, or both. We studied the {alpha}-globin gene abnormalities and the clinical and hematologic features of Chinese patients with hemoglobin H disease in Hong Kong.

Methods We assessed the clinical features, hematologic values, serum ferritin levels, and liver function of 114 patients with hemoglobin H disease. We also performed echocardiography and magnetic resonance imaging of the liver and examined the two pairs of {alpha}-globin genes.

Results Hemoglobin H disease in 87 of the 114 patients (76 percent) was due to the deletion of three of the four {alpha}-globin genes (––/–{alpha}), a combination termed the deletional type of hemoglobin H. The remaining 27 patients (24 percent) had the nondeletional type of hemoglobin H disease, in which two {alpha}-globin genes are deleted and a third is mutated (––/{alpha}{alpha}T). All 87 patients with the deletional type of hemoglobin H were double heterozygotes in whom there was a deletion of both {alpha}-globin genes from one chromosome, plus a deletion of the {alpha}1 or {alpha}2 gene from the other chromosome (––/{alpha}– or ––/–{alpha}). A variety of mutated {alpha}-globin genes was found in the patients with nondeletional type of hemoglobin H disease. Patients with the nondeletional type of the H disease had more symptoms at a younger age, more severe hemolytic anemia, and larger spleens and were more likely to require transfusions than patients with deletional hemoglobin H disease. The severity of iron overload was not related to the genotype.

Conclusions Chinese patients in Hong Kong with the nondeletional type of hemoglobin H disease have more severe disease than those with the deletional type of the disease. Iron overload is a major cause of disability in both forms of the disease.


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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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