6560 Atypical Diabetes Mellitus in a Mother-Son Pair with Multiple Autoimmune Conditions & Pathogenic Variant in BCL11B Inherited from the Mother

Abstract Disclosure: R. Elrajabi: None. N. Gurtunca: None. The etiology of diabetes can be challenging to determine at times and misdiagnosis is common in all age groups. To provide the right treatment and enhance glycemic control, which results in better outcomes and fewer comorbidities, an accurate diagnosis is crucial. We describe a mother-son pair who share a pathogenic variant in BCL11B gene with multiple autoimmune conditions including atypical autoimmune DM. A 13 year old young boy with a history of 33-week prematurity, developmental delay, autoimmune hypothyroidism, and vitiligo presented with concerns for DM given mother’s recent diagnosis of DM treated with Metformin and GLP-1 receptor agonist with poor control of her DM. His mother has a learning disability, hypothyroidism, alopecia totalis, vitiligo and hypertension. Interestingly, he and his mother share a genetic variant in BCL11B gene detected on whole exome sequencing sent as part of the workup of developmental delay. His weight and height were in the 13.5% and 13.9% centiles, respectively. He has vitiligo, but other than that, the physical examination was unremarkable. He is prepubertal. HbA1c was high, 6.4% despite the presence of anemia. An oral glucose tolerance test (OGTT) was consistent with DM as was his repeat HbA1c of 7.1%. He had elevated IA 2, zinc transporter 8, and GAD 65 antibodies, all consistent with autoimmune DM. He was admitted to the hospital and started on both long-acting and short acting insulin via multiple daily injections. BCL11B is a transcription factor that is expressed in all T cells and regulates important processes involved in T cell growth, survival, and function, including Treg cells and Foxp3 activity. Autoimmune diseases have been linked to abnormal Treg activity and Foxp3 deficiency. BCL11B functions as a checkpoint required for T cell lineage commitment while minimizing natural killer cell potential. Impaired BCL11B activity at a young age result in severe whole-body autoimmunity, defined by a fully stimulated immune system similar to animals lacking functioning Treg cells. DM associated with BCL11B variant has not previously been reported. If we follow the theory that autoimmunity affects beta cell function or mass, this patient's and his mother's DM and autoimmune disorders are most likely connected to the BCL11B variation they share. Presentation: 6/2/2024