Hb Chapel Hill or Alpha2 74(EF3) Asp>Gly, a mildly unstable variant found in a Chinese family

Abstract

Background: Hb Chapel Hill [Alpha2 74(EF3) Asp > Gly] results from an GAC > GGC substitution at codon 74 of the HBA1 or HBA2 genes. Hb Chapel Hill has not been reported since 1986.

Methods: A heterozygous mutation, HBA2: c.224A > G, was identified in the proband, her father and sister. We compared the haematological and clinical data of this family with the data reported in the limited number of individuals.

Results: Having excluded iron deficiency, the Hb Chapel Hill was asymptomatic in heterozygous state. The cases presented here characterize cases in new techniques including capillary electrophoresis (CE). Two aberrant peaks were identified by CE, a major peak migrating in the zone 7 that correspond to Hb Chapel Hill (α^{Chapel Hill} ₂β₂) and a minor peak migrating in the zone 1 that correspond to Hb Chapel Hill2 (α^{Chapel Hill} ₂δ₂). Focusing on the variant expression, the Hb Chapel Hill plus Hb A2 variant were around 18.9-20.6% of total Hb in three members.

Conclusion: This data will be useful for providing up-to-date and high quality information on the Hb Chapel Hill.

Keywords: Chinese‌; HBA2‌; Hb Chapel Hill; capillary electrophoresis; hemoglobin variant; mildly unstable Hb; rare mutation; α-thalassemia‌.