Germline mosaicism in an α-thalassemia family: incidental identification by prenatal ultrasound.

What's already known about this topic? In almost all cases of Hb Bart's hydrops fetalis, alpha(0)-thalassemia can be confirmed by testing of parental blood. Germline mosaicism occurs most of the time in autosomal dominant and X-linked recessive disorders. What does this study add? The present case is the first documentation of germline mosaicism for an alpha-thalassemia deletion. Since almost all fetuses affected with Hb Bart's hydrops fetalis present with cardiomegaly on ultrasound, sonographers in regions with high alpha-thalassemia prevalence should be sensitive to the cardiothoracic ratio.