Hb H Hydrops Fetalis Syndrome Caused by Association of the - -(SEA) Deletion and Hb Constant Spring (HBA2: c.427T > C) Mutation in a Chinese Family.

Hb Constant Spring (Hb CS; HBA2: c.427T > C) is an unstable hemoglobin (Hb) variant that results from a nucleotide substitution at the termination codon of the α2-globin gene. Compound heterozygosity for α(0)-thalassemia (α(0)-thal) and Hb CS (- -(SEA)/α(CS)α) results in Hb H/Hb CS disease, which is generally characterized with mild hemolytic anemia, jaundice, and splenomegaly. Here, we describe one case with Hb H/Hb CS disease that presented with fetal anemia and fetal hydrops, known as Hb H (β4) hydrops fetalis. This is the first report of fetal hydrops caused by association of the - -(SEA) deletion and the α(CS)α mutation. Our study highlights the significance of watchful observation using a serial ultrasound method and care of pregnant women who have fetuses found to carry Hb H/Hb CS disease during pregnancy, to guard against the occurrence of fetal hydrops.