MON-253 49,XXXXY Syndrome with Reversible Type 2 Diabetes

Abstract Disclosure: C. Pillai: None. The karyotype 49,XXXXY is a rare and more severe form of Klinefelter syndrome. It generally presents with ambiguous genitalia, intellectual disability, and skeletal/facial abnormalities. It is seen in a frequency of 1:85,000 to 100,000 live births. Unlike traditional Klinefelter syndrome, there is no strong association with Type 2 diabetes in the literature and few cases discuss long term management of patients with both conditions. I present a case of a patient who has developed Type 2 Diabetes and his management. A 16-year-old boy with a karyotype of 49,XXXXY presented with polydipsia and bedwetting for two weeks. He was found to have hyperglycemia with an A1c of 8.5. He initially started on long-acting basal insulin and metformin. Antibody testing for GAD, islet, and insulin antibodies were negative. His father has type 2 DM. He had obesity and a diet high in carbohydrates on diagnosis. Family changed his diet by limiting his carbohydrates, and he was weaned off insulin and eventually also metformin. He has been insulin-free for 4 years and off metformin for 3 years. His most recent A1c is 5.7. Family reported he received testosterone injections as a neonate as well as had two surgeries on his feet. Because of the high rate of hypogonadism in this population, an LH level was collected and was 32.3 IU/L with a testosterone level of 118 ng/dl. He started testosterone therapy on his second visit. His mental development is delayed. He had a characteristic facial appearance with prognathism, a widened nasal bridge, and strabismus. His height is 68 inches, which was normal for his mid-parental height. Lessons: 49,XXXXY syndrome is a rare syndrome, and insulin resistance is not as commonly reported as Klinefelter syndrome. Appropriate screening and early treatment should still be considered for Type 2 DM. Presentation: Monday, July 14, 2025