Rett syndrome complicated by diabetes mellitus type 1.

Summary: Rett syndrome (RS) is an X-linked neurodevelopmental disorder primarily affecting females. RS and diabetes mellitus (DM) type 1 are rare disorders with distinct etiologies. Although some cases of RS complicated by DM type 1 have been reported, the association between these distinct conditions is poorly understood and warrants further studies to elucidate the underlying mechanisms and inform clinical management. We report the case of a 10-year-old girl diagnosed with RS and DM type 1. The patient initially presented at 3 years of age with polydipsia, polyuria and decreased appetite over several weeks. Physical examination showed signs of dehydration, and laboratory evaluation revealed hyperglycemia, elevated HbA1c, glycosuria, ketonuria and low C-peptide levels. Anti-glutamic acid decarboxylase antibodies were positive, confirming autoimmune DM type 1. Fluid resuscitation and insulin therapy were initiated with good glycemic control on continuous subcutaneous insulin infusion. A review of her history revealed normal early developmental milestones, including the onset of stereotypical hand movements at 3 years, communication impairment and seizures at 4 years and a diagnosis of autism spectrum disorder. At 10 years of age, genetic testing revealed a pathogenic MECP2 mutation. Clinical features, including breathing abnormalities, bruxism, abnormal tone and inappropriate laughing, met the diagnostic criteria for RS. This is the reported first case of RS with a confirmed MECP2 mutation complicated by DM type 1. Our case report contributes to the increasing evidence supporting the potential association between RS and DM type 1. Learning points: There is a possible link between RS and DM type 1. This is the first case report of RS with a confirmed MECP2 mutation complicated by DM type 1. In cases where patients with RS develop diabetic ketoacidosis, it may manifest as mild acidosis or normal pH despite the presence of high blood sugar levels and dehydration.