Prenatal diagnosis of 13q- syndrome in a fetus with holoprosencephaly and thumb agenesis.

Partial deletion of the long arm of one of the chromosomes 13 is an exceedingly rare condition. We report such a case in a 32-week fetus presenting with polyhydramnios, growth restriction and multiple structural defects including alobar holoprosencephaly, facial abnormalities, clubfoot, clinodactyly and thumb agenesis. Fetal blood sampling revealed a 46,XY, del(13)(q22 --> qter) abnormal male karyotype. Postmortem examination confirmed the prenatal findings and showed other manifestations of the syndrome. To our knowledge, this case represents the first in which the prenatal ultrasound detection of holoprosencephaly in association with distal limb abnormalities led to the prenatal diagnosis of the 13q- syndrome.