Lumbosacral Polyradiculoneuropathy in a Patient With Autoimmune Polyendocrine Syndrome Type 3A

Background Autoimmune polyendocrine syndrome type 3A is characterized by immune-mediated endocrine dysfunction involving autoimmune thyroid disease and type 1 diabetes mellitus. Neurological involvement is uncommon. We describe a patient with autoimmune polyendocrine syndrome type 3A who developed painful lumbosacral polyradiculoneuropathy with inflammatory features, highlighting the co-occurrence of autoimmune endocrine and neurological disorders. Case Presentation A 25-year-old woman presented with progressive lumbosacral pain, dysuria, and bilateral lower-limb neuropathic pain. She had type 1 diabetes mellitus and a history of autoimmune thyroid disease. Lumbar magnetic resonance imaging showed thickening and enhancement of the lumbosacral nerve roots, and electrophysiologic testing supported peripheral nerve involvement. Genetic testing did not identify related pathogenic variants. Intravenous immunoglobulin provided only transient relief, whereas corticosteroid therapy was associated with substantial clinical improvement but was limited by hyperglycemia; azathioprine was subsequently introduced as a steroid-sparing agent. Discussion Diabetes-associated neuropathies, Sjögren syndrome, nutritional deficiency, vasculitis, and hereditary causes were carefully evaluated and considered less likely. The subacute painful presentation, lumbosacral nerve-root enhancement, mildly elevated cerebrospinal-fluid protein, and electrophysiological findings were compatible with a possible inflammatory polyradiculoneuropathy. Conclusion Painful lumbosacral polyradiculoneuropathy may occur in patients with APS-3A and may represent a potentially treatable neurological manifestation. Their coexistence may reflect a shared autoimmune predisposition, although an increased risk of inflammatory neuropathy in APS-3A has not been established.