Cerebellar ataxia and depression associated with anti-RhoGTPase-activating protein 26 antibody: A case report.

Neuroimmune disorders associated with anti-RhoGTPase-activating protein 26 immunoglobulin G (IgG) autoantibodies (ARHGAP26; also termed anti-Ca) are infrequent and manifest a significant diversity in clinical presentations, including cerebellar ataxia, psychotic disorders, and cognitive impairments. This case report describes a middle-aged female who developed subacute cerebellar ataxia and depression. Detection of anti-ARHGAP26 IgG in both serum and cerebrospinal fluid (CSF) led to her diagnosis of primary autoimmune cerebellar ataxia, supported by her medical history of Sjögren's syndrome and the identification of CSF-specific oligoclonal bands. After undergoing sequential immunotherapy including corticosteroid, intravenous immunoglobulin, plasma exchange, mycophenolate mofetil and rituximab, her Scale for the Assessment and Rating of Ataxia score improved from 28.5 to 18, demonstrating partial recovery. This case highlights the necessity of considering an autoimmune etiology in patients presenting with subacute cerebellar ataxia and suggests that testing for ARHGAP26-IgG is warranted also when psychocognitive impairment is clinically evident. Early initiation of immunotherapy is important to enhance patient outcomes.