Which genetic condition is associated with an ultrasound finding of a cloverleaf skull?

The genetic condition associated with an ultrasound finding of a cloverleaf skull is thanatophoric dysplasia type 2. Cloverleaf skull, also known as oxycephaly, is characterized by an abnormal shape of the skull due to premature fusion of the cranial sutures. This condition is typically seen in certain skeletal dysplasias, particularly thanatophoric dysplasia, which is a severe form of skeletal dysplasia leading to significant growth and developmental issues.

Thanatophoric dysplasia type 2 is specifically associated with mutations in the FGFR3 gene and can present with distinct ultrasound findings, including the cloverleaf skull. This finding is particularly notable in the context of fetal imaging, as it indicates a severe disruption in normal skull morphology and can be an important marker for diagnosis.

Other conditions, such as trisomy 21, skeletal dysplasia in general, and Down syndrome, do not specifically exhibit a cloverleaf skull as a hallmark finding in prenatal assessments. Trisomy 21 (Down syndrome) may present with other craniofacial anomalies, but the cloverleaf skull is not characteristic of it. Thus, thanatophoric dysplasia type 2 is the most accurate association for this particular ultrasound finding.