ODP373 A Tale of Two Syndromes: Coexistence of Russell-Silver and Klinefelter Syndrome

BACKGROUND/AIMS: Klinefelter syndrome is a common condition characterized by an extra X chromosome, tall stature, gynecomastia, and hypogonadism. Russell-Silver syndrome is a rare disorder characterized by intrauterine growth restriction, poor growth after birth, and triangular facies. The coexistence of Russell-Silver and Klinefelter syndrome has so far not been reported in the literature. This study aimed to characterize the phenotype of such an individual. METHODS: Clinical and endocrinal investigations were performed and followed by pathogenic variant screening of candidate genes. RESULTS: An 8-year-old boy was evaluated for short stature. He was a former 27-week preemie who had postnatal growth failure. His mean parental height was5'6" (66 inches). His growth chart showed that he was below the 0. 01% percentile in both height and weight for age. He had behavioral issues. On physical exam, he had high riding prepubertal testes and proportional limbs. He was evaluated by both genetics and endocrine. His bone age was delayed by 4 years. He passed his growth hormone stimulation test. He had a nondiagnostic bone survey. His chromosomal microarray showed an XXY karyotype. Further testing was collected because it did not explain his short stature. He was found to have maternal uniparental disomy of 7q32.2. He was started on growth hormone and his most recent growth velocity was 4 cm a year. He continues to be below the 0. 01% percentile in both height and weight for age Conclusion: This is the first report on a patient with the coexistence of Russell-Silver and Klinefelter syndrome. It shows that the short stature and postnatal growth of Russell-Silver syndrome is the prevailing phenotype in this rare combination. Presentation: No date and time listed