Secondary Mutation (c.94_95delAG) in A −α^3.7 Allele Associated with Hb H Disease in Two Unrelated African American Individuals Homozygous for the −α^3.7 Deletion (−α^3.7/−α^3.7T)

Abstract

Hb H disease is rarely seen in individuals of African descent although α-thalassemia (α-thal) is common in this population. Usually α-thal is due either to heterozygosity or homozygosity for the −α^3.7 deletion in this population. We report Hb H disease that is caused by a frameshift mutation on one −α^3.7 allele in two unrelated individuals homozygous for the −α^3.7 deletion. These two cases highlight the importance of further investigation by direct sequencing of the –α^3.7 allele when the thalassemic phenotype does not correlate with the genotype obtained by initial molecular testing.

• Hb H disease
• α-Thalassemia (α-thal)
• −α^3.7 Deletion