Blended Phenotypes From a SERPINA 11 Pathogenic Variant Over Underlying Immune Fetal Hydrops: A Rare Case Report and Literature Review

Fetal hydrops can stem from immune or nonimmune causes. Immune causes often involve red cell alloimmunization, whereas nonimmune causes encompass structural malformations, aneuploidy, infections, lymphatic system disorders, genetic syndromes, and more. In a rare and complex case, we encountered a fetal hydrops presentation characterized by blended phenotypes, indicating both a genetic and an underlying immune etiology. The mother, Rhesus negative, presented with a history of adverse obstetric events. At 21 weeks, the current fetus was diagnosed with hydrops. Maternal blood tests unveiled Rhesus alloimmunization, featuring a positive indirect Coombs test at a 1:512 dilution and the presence of anti-D, anti-C, and anti-E antibodies. Fetal blood sampling revealed an O-positive blood group with a hemoglobin level of 10 gm/dL. Despite administering intrauterine transfusion to the fetus, there was no improvement; instead, the fetal hydrops worsened, accompanied by the emergence of nuchal and axillary masses. Exome sequencing of fetal DNA revealed the fetus was homozygous for a pathogenic variant in the <i>SERPINA11</i> gene and compound heterozygous for a pathogenic variant in the PIEZO1 gene. Furthermore, the combination of pathogenic variants in <i>SERPINA11</i> and <i>PIEZO1</i> genes has not been described in cases of fetal hydrops before. This case posed significant challenges in management due to the concurrent presence of both immune and nonimmune hydrops. We describe some of the diagnostic challenges faced in clinical management of this case.