Transient hydrops fetalis in a prenatally diagnosed pentasomy X?

Numerical abnormalities of sex chromosomes are seen approximately 1 in 400 live births. Pentasomy X is a very rare chromosomal abnormality and it is defined as presence of five X chromosomes instead of two. Prenatal sonographic features have rarely been described in the literature before. Here we present a non-immune fetal hydrops diagnosed during the 17th week of gestation. Ultrasonographic examination revealed subcutaneous edema, pleural effusion and ascites, and also clinodactyly of the fifth fingers of both hands. The fetal karyotype was assessed as 49,XXXXX (pentasomy X) in two different culture flasks. Hydropic signs regressed at 21 weeks' gestation. Prenatal diagnosis may not be possible usually for this rare chromosomal abnormality. Every anomaly detected prenatally, such as transient hydrops, may help us to diagnose pentasomy X.