Kagami-Ogata syndrome (KOS) is a rare and potentially underdiagnosed imprinting disorder caused by paternal uniparental disomy for chromosome 14 or microdeletions and epimutations involving differentially methylated regions (DMRs) at 14q32.2. Depending on phenotypic expression, KOS may mimic trisomy 18 and asphyxiating thoracic dysplasia. Therefore, awareness is essential for prenatal diagnosis. Coat hanger ribs as seen by x-rays have been reported as s pathognomonic sign but have not been reported prenatally. Herein we present images of the coat hanger ribs as seen by low-dose computerized tomography (CT) as well as detailed imaging of the multiple phenotypic features by ultrasound and MRI of KOS in two cases seen prenatally. Case 1: G1P0 singleton pregnancy had fetal echocardiogram at 25 weeks due to concern for congenital heart disease, thickened nuchal fold and thickened skin of the thoracic wall. The exam showed left superior vena cava draining to coronary sinus, dilated right atrium and right ventricle, total anomalous pulmonary venous return, and hydrops. Skin edema was redemonstrated by follow up US at 29 weeks. Fetal MRI and follow-up US at 32 weeks showed polyhydramnios, diffuse skin edema, prominent cheeks and frontal bossing by 3D US, mild shortening of the ulna and right clubfoot, and a bell-shaped thorax by MRI. Chromosomal microarray was positive for terminal deletion of 14q32.2, consistent with KOS. Coat hanger ribs were present on postnatal x-rays. The patient is G-tube and tracheostomy tube dependent, has global developmental delay, neuromuscular scoliosis, left hip subluxation, wrist contractures and planovalgus feet at the age of 2 ½ years. Case 2: G3P1, singleton pregnancy with negative non-invasive prenatal testing (NIPT). US performed at 29 weeks showed polyhydramnios, clenched hands, and bell-shaped small thorax. Multimodality fetal imagin (US, MRI and CT) at 32 weeks showed a narrowed elongated thorax by US and MRI but ribs were poorly visualized. Additional anomalies included polyhydramnios, rhizomelic bone shortening, clenched hands, and prominent cheeks by 3D US. Low-dose CT showed coat hanger ribs. Postnatal x-rays confirmed coat hanger ribs and other abnormalities. Postnatal genetic testing showed paternal uniparental disomy for chromosome 14, consistent with KOS. The patient has restrictive lung disease due to hypoplastic thoracic cage, hypotonia, scoliosis, developmental delay, and umbilical hernia at 13 months.
SPR 2023 Annual Meeting & Postgraduate Course