Prenatal diagnosis of thanatophoric dysplasia: A case report

Thanatophoric dysplasia (TD) is a rare and uniformly lethal skeletal dysplasia caused by activating mutations in the FGFR3 gene located on chromosome 4p16.3. It represents one of the most severe forms of osteochondrodysplasia diagnosed in the prenatal period. Although molecular genetic testing confirms the diagnosis, characteristic imaging findings frequently allow reliable prenatal identification. Two phenotypic subtypes are described: type I, characterized by curved long bones, and type II, associated with a cloverleaf skull deformity.

We report the case of a 26-year-old nulliparous woman with an unsupervised pregnancy who presented at 34 weeks of gestation with threatened preterm labor. Ultrasound examination revealed macrocephaly, severe micromelia with markedly shortened and curved femurs demonstrating a classical ‘telephone receiver’ appearance, a narrow thorax, and polyhydramnios. Type I thanatophoric dysplasia was suspected and subsequently supported by fetal computed tomography. Due to contextual and legal constraints regarding termination of pregnancy, expectant management was adopted. Intrauterine fetal demise occurred at 35 weeks of gestation, followed by vaginal delivery of a stillborn female neonate weighing 1940 g. Postmortem radiography confirmed the characteristic skeletal abnormalities.

This case highlights the pivotal role of prenatal imaging in diagnosing lethal skeletal dysplasias, particularly in settings where molecular testing and termination options may be limited.