Objective: To discuss a slowly progressive case of anti-Ca/ARHGAP26 autoantibody-associated cerebellar ataxia.

Background: Anti-Ca/ARHGAP26 autoantibody-associated cerebellar ataxia was first identified in 2010 (1). Since then, only five other cases have been published (2). Within these, symptoms varied from ataxia, dysarthria, nystagmus, myoclonic jerks, memory impairment, depression, nausea and dizziness. Treatment included high dose steroids, intravenous immunoglobulins, plasma exchange, immunoadsorption and immunosuppressive treatment.

Methods: Cell based indirect immunofluorescence performed on monkey cerebellum tested positive for Rho GTPase-activating protein 26, which is consistent with autoantibody-associated cerebellar ataxia.

Results: Triggered by voluntary, targeted movements, a 79-year old male showed acute worsening of myoclonic jerks which initially appeared 27 years ago. The previously documented bradykinesia with freezing of gait and postural imbalance was now accompanied by morning stiffness, dysarthria, hypomimia and hypophonia. Furthermore, a cognitive decline with forgetfulness and involuntary loss of urine was now evident. On exam, there was rigidity of the left arm and both legs, resting tremor in all extremities, irregular postural tremor in both arms as well as stimulus sensitive action myoclonus of all limbs and apraxia. An urinary tract infection was treated antibiotically. Shortly thereafter, all symptoms improved spontaneously to the level prior to acute worsening. The patient was never treated with immunosuppressants.

Conclusions: Our patient offers a new spectrum of anti-Ca/ARHGAP26 autoantibody-associated cerebellar ataxia. The slow progression without any immunosuppressive treatment over 27 years and the accompanying parkinsonian features are novel findings and have never been described before. Whether immunosuppressive treatment influences the course of disease or if it’s a fluctuating course of disease itself remains thus unclear.

References: (1) Jarius, S., Wandinger, K. P., Horn, S., Heuer, H. & Wildemann, B. A new Purkinje cell antibody (anti-Ca) associated with subacute cerebellar ataxia: immunological characterization. J. Neuroinflammation 7, 21 (2010). (2) Wallwitz, U. et al. From dizziness to severe ataxia and dysarthria: New cases of anti-Ca/ARHGAP26 autoantibody-associated cerebellar ataxia suggest a broad clinical spectrum. J. Neuroimmunol. 309, 77–81 (2017).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/slowly-progressive-anti-ca-arhgap26-autoantibody-associated-cerebellar-ataxia-over-27-years-without-immunosuppressive-treatment/