A New Case of Lethal Congenital Contracture Syndrome Type 3 With Hyperinsulinism and Optic Atrophy.

Lethal congenital contracture syndrome 3 (LCCS3, MIM #611369) is a rare autosomal recessive neuromuscular disorder caused by biallelic loss-of-function (LOF) variants in PIP5K1C, reported in only two families to date. It typically presents with severe fetal akinesia, arthrogryposis multiplex congenita, and perinatal lethality due to respiratory insufficiency case. Herein, we report a new case with survival beyond birth. Prenatal findings included clubfeet with preserved amniotic fluid volume and fetal movements. The infant was delivered by cesarean section at 37 + 7 weeks following breech presentation and developed respiratory distress requiring 14 days of ventilatory support. Physical examination revealed bilateral talipes equinovarus, flexion contractures of the knees, restricted hip mobility, clenched hands with flexion contractures of the third and fourth fingers, and hyperextension of the second and fifth fingers. Neurologically, he had encephalopathy, profound hypotonia with a frog posture, and abnormal neonatal reflexes with a discontinuous background pattern on cerebral function monitoring. Additional observed features were bilateral optic atrophy and hyperinsulinemic hypoglycemia responsive to Diazoxide. Trio genome sequencing identified a homozygous pathogenic splice-site variant in PIP5K1C (c.1127+1G>A, NM_012398.3). The infant died at 6 months from multisystemic failure. Further studies are warranted to elucidate the pathomechanisms underlying the PIP5K1C defect and its phenotypic consequences.