Hb Tarrant [α126(H9)Asp→Asn; HBA2: c.379G > A (or HBA1)] in a Chinese Family as a Cause of Familial Erythrocytosis.

Hb Tarrant [α126(H9)Asp→Asn; HBA2: c.379G > A (or HBA1)], is a rare high oxygen affinity hemoglobin (Hb) variant that causes erythrocytosis, previously described in a few Mexican-American families. Here we report the first Chinese family with this Hb variant presenting with unexplained familial erythrocytosis. No evidence of hemolysis was seen. A locally adapted approach to the diagnostic process in clinical laboratories is discussed. Molecular analysis has an important role in confirmation of the diagnosis. Proper identification of this rare but clinically significant Hb variant is helpful for family counseling and will help to guide appropriate management of absolute erythrocytosis.