Sporadic Larsen syndrome in a preterm female originally diagnosed as positional deformities due to oligohydramnios

Few reports describe incidental prenatal diagnosis of sporadic Larsen syndrome by ultrasound, but none of these discuss coincidental oligohydramnios or an association with fetal growth restriction. A 28-year-old woman had prolonged rupture of membranes causing marked oligohydramnios at 32 weeks gestation in her first pregnancy. Labor was induced by vaginal prostaglandins and oxytocin infusion after dexamethasone administration because of concern about placental abruption. She delivered vaginally a live female infant weighing 1960 g (< 10th percentile) with multiple skeletal malformations and characteristic facies originally suspected as positional. Newborn x-rays, however, established the diagnosis of Larsen syndrome with bilateral dislocations of the hips, knees (genu recurvatum), and ankles (club foot). The neonatal karyotype was 46,XX. Parental examination and family history were unremarkable. The newborn did well with bilateral lower extremities cast. Postnatal diagnosis of Larsen syndrome should be suspected in neonates with multiple skeletal abnormalities following oligohydramnios.