Neurochondrin immunoglobulin G - Associated myelopathy - Ataxia syndrome

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

BACKGROUND AND PURPOSE

Neuronal autoantibodies can support the diagnosis of primary autoimmune cerebellar ataxia (PACA). Knowledge of PACA is still sparce. This article aims to highlight the relevance of anti-neurochondrin antibodies and possible therapeutical consequences in people with PACA.

METHODS

This is a case presentation and literature review of PACA associated with anti-neurochondrin antibodies.

RESULTS

A 33-year-old man noticed reduced control of the right leg in May 2020. During his first clinic appointment at our institution in September 2021, 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 3 months the symptoms progressed. An initial cerebral magnetic resonance imaging, June 2020, was normal, but follow-up imaging in October 2021 and July 2022 revealed marked cerebellar atrophy (29% volume loss). Cerebrospinal fluid analysis showed lymphocytic pleocytosis of 11 x 10³ /L (normal range 0-4) and oligoclonal bands type II. Anti-neurochondrin antibodies (immunoglobulin G) were detected in serum (1:10,000) and cerebrospinal fluid (1:320, by cell-based indirect immunofluorescence assay and immunoblot, analysed by the EUROIMMUN laboratory). After ruling out alternative causes and neoplasia, diagnosis of PACA was given and immunotherapy (steroids and cyclophosphamide) was started in January 2022. In March 2022 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 unrecognized 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 are attainable.

Case Report: Alzheimer's Dementia Associated With Cerebrospinal Fluid Neurochondrin Autoantibodies

Background

Neurochondrin autoimmunity is a rare disorder mainly associated with cerebellar and vestibular syndromes. Our report aims to enlarge its phenotypic spectrum to encompass major cognitive disorder with very late onset never before reported in conjunction with neurochondrin antibodies.

Methods

We describe the case of an 85-year-old woman who presented in our memory clinic. Retrospective analysis of patient records included cerebrospinal fluid (CSF) analysis, magnetic resonance imaging (MRI), and neuropsychological testing using the CERAD-plus.

Results

Because of her unknown onset of progressive cognitive dysfunction in conjunction with speech and language problems, we decided to take an extensive differential diagnostic approach including a search for neural autoantibodies potentially involved in cognitive impairment. Our patient presented serum and CSF neurochondrin autoantibodies. Further CSF analysis revealed elevated tau and ptau 181 protein as well as a reduced Aß42/40 ratio in CSF, thus matching a biomarker profile of Alzheimer's disease (AD). Neuropsychological tests revealed predominant and severe deficits in verbal and visual memory. Her MRI showed reduced parietal and cerebellar brain volume.

Discussion

Taken together, this case reveals the novelty of a patient with a CSF-based and typical clinical and imaging profile of AD. She is also likely to have neurochondrin autoimmunity, as we detected neurochondrin autoantibodies in her CSF; we therefore diagnosed AD dementia associated with neurochondrin antibodies. Our case expands the spectrum of neurochondrin autoimmunity to disorders involving major cognitive disorder such as AD dementia. Furthermore, we speculate that neurochondrin autoimmunity might have triggered an acceleration of AD symptoms as its onset was reported only after a short 6-month interval via a synergistic or negatively additive hybrid mechanism of action between neurodegeneration and autoimmunity.