Rhombencephalosynapsis in a severely polymalformed fetus with non-mosaic tetrasomy 9p, in intracytoplasmic-sperm-injection pregnancy.

Case reportA fetus with rhombencephalosynapsis and prenatally diagnosed tetrasomy 9p is reported. Chromosomal analysis from amniocyte culture revealed non-mosaic supernumerary chromosome identified as isochromosome 9p (9p24-->q13::q13-->p24). Ultrasound scan revealed intrauterine growth retardation, renal anomalies, cardiac anomalies, ventriculomegaly, and agenesis of cerebellar vermis with fusion of the cerebellar hemispheres.ConclusionAlthough most cases of cerebellar vermis agenesis in tetrasomy 9p are described with cystic malformation such as Dandy-Walker anomaly, our case indicates that this chromosomal disorder should be taken into account in fetuses with the development of cystic and non-cystic malformations of cerebellar vermis and posterior fossa.