Anti-neurochondrin antibody as a biomarker in primary autoimmune cerebellar ataxia - a case report and review of the literature

INTRODUCTION Neuronal autoantibodies can support the diagnosis of primary autoimmune cerebellar ataxia (PACA). METHODS Case presentation and literature review of PACA associated with anti-neurochondrin antibodies. RESULTS A 33-year-old man noticed 05/20 reduced control of the right leg. First at our hospital 09/21, he complained about gait imbalance, fine motor disorders, tremor, intermittent diplopia and slurred speech. He presented a pancerebellar syndrome with stance, gait and limb ataxia, scanning speech and oculomotor dysfunction. Within three months the symptoms progressed. Initial cerebral magnetic resonance imaging (MRI) 06/20 was normal, but follow-up imaging 10/21 and 07/2022 revealed marked cerebellar atrophy (29% volume loss). Cerebrospinal fluid (CSF) analysis showed lymphocytic pleocytosis of 11 M/L (normal range 0-4), and oligoclonal bands type II. Anti-neurochondrin antibodies (IgG) were detected in serum (1:10'000) and CSF (1:320, by cell-based indirect immunofluorescence assay and immunoblot, analysed by EUROIMMUN laboratory). After ruling out alternative causes and neoplasia, diagnosis of PACA was given and immunotherapy (steroids and cyclophosphamide) was started 01/22. In 03/22 a stabilization of disease was observed. CONCLUSION Cerebellar ataxia associated with anti-neurochondrin antibodies has only been described in 19 cases; however, the number of unrecognised PACAs may be higher. As anti-neurochondrin antibodies target an intracellular antigen and exhibit a mainly cytotoxic T cell mediated pathogenesis, important therapeutic implications may result. Because of the severe and rapid clinical progression, aggressive immunotherapy was warranted. This case highlights the need for rapid diagnosis and therapy in PACA, as stabilization and even improvement of symptoms is attainable.