Thanatophoric Dysplasia A Case Report Diagnosis and Management

Abstract: Thanatophoric dysplasia (TD) is the most common of the lethal skeletal dysplasias presented in the second trimester. Two subtypes exist: TDI has short curved femurs with or without a clover leaf skull; TDII has straight, longer femurs and generally a more severe clover leaf skull. Sporadic inheritance with extremely small recurrence risk associated with advanced paternal age (>35years). Mutations in fibroblast growth factor receptor 3 (FGFR3) are the underlying basis for the disorder. There is a strong genotype– phenotype correlation. DNA diagnosis is highly accurate. FGFR3 is also expressed in the brain. Rare survivors are uniformly severely developmentally delayed. The incidence of TD ranges from 0.27 in 10,000 to 0.4 in 10,000 live births. In a large series of 126,000 deliveries occurring at one institution, TD was the most common osteochondrodysplasia observed. We present a case of thanatophoric dysplasia due to its rarity. A 33 y.o. female, G2P1A0 came with polyhydramnion and ultrasonography shown congenital abnormality of the fetus at 29-30 weeks gestational age (GA). Amniocentesis and amnioreduction done at 30 weeks 5 days GA. With the G-binding technique in 40 cells, the chromosome number in each cell obtained is mos 92,XXXX[15]/46,XX [25]. A male baby with 1850 g weight was born at 31 weeks 5 days GA by spontaneous delivery, Apgar scores 3-5, congenital abnormalities (short femur, short humerus, bowel sign, absen nasal bone) which matched with thanatophoric dysplasia type I. In conclusion, Thanatophoric Dysplasia is a congenital, sporadic and the most lethal skeletal dysplasia at birth. Ultrasonography highly indicates the diagnosis of TD. Features like macrocephaly, wide fontanels, micromelia, and telephone receiver like femur, short stubby fingers, deep skin creases, narrow thorax and protuberant abdomen are highly suggestive of thanatophoric dysplasia type I. Keywords: Thanatophoric dysplasia, Fibroblast growth factor receptor 3 (FGFR3) mutation, Short femur, Short humerus, Bowel sign, Absen nasal bone