Prenatal diagnosis of molybdenum cofactor deficiency.

Objectives: To describe the prenatal imaging findings and genetic diagnosis of molybdenum cofactor deficiency (MoCD) in two consecutive pregnancies, highlighting its variable prenatal presentation and diagnostic challenges. Case presentation: MoCD is a rare autosomal recessive metabolic disorder associated with severe neurological impairment and usually diagnosed postnatally. We report a consanguineous couple with two consecutive affected pregnancies. In the first, progressive ventriculomegaly and posterior fossa abnormalities were detected in the third trimester, raising suspicion of an underlying metabolic disorder, which was confirmed by genetic testing. In a subsequent monochorionic monoamniotic twin pregnancy, early imaging was unremarkable, but targeted genetic testing confirmed recurrence in both fetuses. Conclusions: MoCD may present prenatally with progressive central nervous system abnormalities. Combined imaging and molecular testing are essential for diagnosis, particularly in consanguineous couples, enabling timely counseling and reproductive decision-making.