Early prenatal presentation of the cartilage-hair hypoplasia / anauxetic dysplasia spectrum of disorders mimicking recurrent thanatophoric dysplasia.

Three sibling fetuses identified with limb shortening and thoracic narrowing at twelve weeks' gestation on first trimester ultrasound examination are presented. The parents were non-consanguineous, Caucasian, healthy, of normal stature and had a healthy normal daughter. The radiographic abnormalities were highly suggestive of thanatophoric dysplasia, but molecular analysis failed to identify a pathogenic variant in FGFR3. The three fetuses were found to have identical compound heterozygous mutations in RMRP in trans, one inherited from the mother and one from the father. This represents the early prenatal presentation and fetal findings of metaphyseal dysplasia type McKusick (Cartilage-hair hypoplasia; CHH)/anauxetic dysplasia spectrum of disorders.