Discussion
This patient presented with congenital anemia of unknown cause with a history of intrauterine transfusion requirement. Hemolytic markers were strikingly elevated. Reticulocytosis explained the high MCV. The differential diagnosis of congenital hemolytic anemia is wide (supplemental table 2). Maternal-fetal alloimmunization is the most common etiology. There are case reports of fetuses with hydrops fetalis secondary to alloimmunization that were born with a negative IAT (17). We therefore performed extensive blood bank testing that completely rule out alloimmunization. We sent a mucosal DNA NGS inherited hemolytic anemia panel. This test is not affected by the post-transfusion status. CDA was historically diagnosed by RBC property testing and bone marrow morphology. However, with the advent of genetic testing, NGS has become the gold standard to diagnose rare congenital hemolytic anemia, like CDA. The genetic basis of CDAIV was first sequenced nearly ten years ago by Arnaud & al. (2010), who identified two patients with a KLF1 mutation. Twelve patients have been described since. Most show consistent features with onset in the neonatal period (8/12 patients), but delayed diagnoses occur despite accessible technologies (see table 1). We reached a diagnosis within one month of life, which is the fastest CDA diagnosis ever described. In summary, our case highlights a patient with CDA4 de novo mutation with in uteroerythropoietic disturbances requiring transfusion, post-natal hemolytic anemia and combined hyperbilirubinemia transiently refractory to exchange transfusions. Thrombocytopenia has been rarely described in CDAI and CDAIV(18). The transient thrombocytopenia of this patient was considered secondary to exchange transfusions. This case demonstrates the importance of a prenatal referral to hematology and neonatology when hydrops fetalis of unknown etiology is detected for diagnostic and postnatal planning purposes. It is a reminder that it is optimal practice to obtain pre-transfusion blood sampling in an EDTA tube in patients with severe anemia. Finally, it illustrates that the use of NGS technologies can expedite early diagnosis of rare congenital anemia, like CDAIV, allows for anticipatory guidance and consequently reduces anxiety of clinicians and families, while optimizing health care utilization.