Non-immune fetal hydrops: Are we doing the appropriate tests each time?

Non-immune fetal hydrops is diagnosed when there is fluid accumulation in more than one extravascular space. A long list of etiologies has been found in association with non-immune hydrops. Thorough investigations are needed to be able to identify an underlying cause. There are many recent reports indicating that non-immune hydrops can be an extreme presentation of a number of metabolic disorders, mostly lysosomal storage diseases. The fetal hydrops associated with metabolic disorders is usually severe with very thick skin, massive ascitis, other feature could be seen such as contracture deformities, skeletal abnormalities, hepatosplenomegaly, renal abnormalities, and enlarged nuchal translucency. The diagnosis of a metabolic disorder can be done by a variety of different tests: measuring the level of the specific enzyme or metabolite, histological examination of different organs, or mutation identification. An index case is usually needed to confirm the diagnosis. In-utero diagnosis of a metabolic disorder in the absence of an index case is difficult and only available in selected laboratories around the world. In populations with high consanguinity, these diseases are much more commonly present than what we might think. Routine screening for metabolic diseases especially lysosomal storage diseases should be considered in these populations, and definitely in cases of recurrent hydrops in the same family. More efforts should be spent on identifying causative mutations in different ethnic groups. Every effort should be made to identify the etiology in an index case in the family, as this might be the best opportunity for improving future care.