Acute neurological Behçet's disease complicated by a syndrome of inappropriate secretion of antidiuretic hormone.

We report a rare case of acute neurological Behçet's disease (neuro-BD) diagnosed concurrently with systemic Behçet's disease (BD), classified as definite BD, and complicated by syndrome of inappropriate antidiuretic hormone secretion (SIADH). A man in his 60s presented with fever, headache and mucocutaneous lesions including oral aphthae, folliculitis-like rashes, genital ulcers and hyponatraemia. He was diagnosed with BD based on mucocutaneous findings. Brain MRI showed no abnormalities, and cerebrospinal fluid analysis revealed aseptic meningitis, supporting the diagnosis of acute neuro-BD. Laboratory tests confirmed the diagnostic criteria for SIADH. Colchicine monotherapy led to a resolution of the patient's mucocutaneous symptoms, neurological manifestations and hyponatraemia, without the need for corticosteroids or other immunosuppressants. This case suggests a possible association between acute neuro-BD and SIADH and underscores the importance of recognising concurrent neurological and endocrine manifestations in patients with newly diagnosed BD.