Uncommon manifestations of a rare disease: a case of autoimmune GFAP astrocytopathy

BACKGROUND: Manifestations of intractable hyponatremia and hypokalemia in autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy have been rarely reported. CASE PRESENTATION: A 75-year-old male patient presented as the case of syndrome of inappropriate antidiuretic hormone secretion (SIADH) and intractable hypokalemia, showed fever, fatigue, and mental disorders. Signs and symptoms of meningoencephalitis, ataxia, and cognitive abnormalities. Magnetic resonance imaging (MRI) revealed multiple white matter lesions of the central nervous system. He had GFAP-IgG in the cerebrospinal fluid (CSF). After treatment with corticosteroids, his symptoms were alleviated gradually, and the level of electrolytes was normal. However, head contrast-enhanced MRI + susceptibility-weighted imaging (SWI) showed a wide afflicted region, and the serum GFAP-IgG turned positive. Considering the relapse of the disease, ha was treated with immunoglobulin and mycophenolate mofetil (MMF) to stabilize his condition. CONCLUSION: This case showed a rare disease with uncommon manifestations, suggesting that careful examination and timely diagnosis are essential for disease management and satisfactory prognosis.