P451: New familial variant identified in CSDE1-associated neurodevelopmental disorder

information available about additional features or management of SWS in adults.We present a case report of a 35-year-old female with SWS, one of the few documented adults with SWS.Case Presentation: She presented to clinic with a prior clinical diagnosis of osteogenesis imperfecta (OI), which was given in childhood based in part on a history of recurrent fractures and blue sclera.She had not had any previous genetic testing.Her current symptoms included heart palpitations, fatigue, difficulty sleeping, temperature dysregulation, dental problems, and bone fragility.On physical exam, she had short stature, blue sclera, and significant loss of range of motion in most bones with fusions in the fingers, toes, and major long bones throughout.Dual-energy x-ray absorptiometry (DEXA) scan showed osteoporosis and deformity of the right hip and left forearm.In infancy, she experienced feeding and breathing difficulties.She reports her symptoms of difficulty with temperature regulation and recurrent fractures have been life-long.Of note, she has had more than 25 surgeries without complications from anesthesia.Her treatment in childhood included bisphosphonate treatments, both orally and via infusion, but had not occurred for many years.She was incidentally identified to have a brain aneurysm at the age of 34.Diagnostic Workup: Initial genetic testing included an OI and bone fragility panel, which was non-diagnostic and identified a variant of uncertain significance (VUS) in COL1A2 at c.329C>T (p.Pro110Leu).This missense change replaces proline (neutral, non-polar) with leucine (neutral, non-polar) and is not expected to disrupt protein function.Given the non-diagnostic result, exome sequencing (ES) was ordered, which identified a homozygous pathogenic variant in LIFR at c.756dup (p.Lys253*), consistent with a diagnosis of SWS.