Diagnostic anténatal d'un cas de nanisme thanatophore type I

Thanatophore nanism is an uncommon osteochondrodysplasia classified in type I and type II. It is due to a mutation of the FGFR 3 (fibroblast growth factor receptor 3) located on the short arm of chromosome 4. It is a morphological anomaly always lethal whose definitive diagnosis calls for molecular biology. But medical imaging must be on the front line in the early antenatal screening in order to propose the pregnant patient a therapeutic interruption of the pregnancy to avoid any psychological and obstetrical traumatism. We report the case of a 33-year-old-woman, nulliparous without any particular history and in whom the ultrasound scan performed in the 26th week of amenorrhea in the context of a classical prenatal surveillance allowed the diagnosis of thanatophore nanism type I with very suggestive images of fetal dysmorphism. It was about a macrocephalia, a narrowness of the thoracic cage contrasting with a prominent abdomen and an extremely shortened aspect of limbs associated with curved femurs. Since the patient refused the therapeutic interruption of the pregnancy, we supervised the progression of the pregnancy until vaginal delivery. She gave birth to a dwarf baby which was 34 cm long and weighed 2600 g. It died 30 minutes after birth.