Objective: SCAR10/ Adult-onset autosomal recessive cerebellar ataxia is an exceptionally rare form of ataxia, caused by mutations in the ANO10 gene and the specific genotype–phenotype

correlation of the disease is not well understood. We present a case of ANO10 gene mutation causing unusual manifestations of SCAR10.

Background: The autosomal recessive cerebellar ataxias comprise a diverse group of neurodegenerative disorders. Recent studies have identified mutations in the anoctamin 10 gene (ANO10) as a cause of autosomal recessive spinocerebellar ataxia type 10.

Method: A 46-year-old lady presented with complaints of dysarthria, ataxia and recurrent falls of 1 year duration with a history of RBD 2 years duration. There was no history suggestive of parkinsonism, ataxia, or dystonia in the family. Clinical examination revealed scanning dysarthria, hyperreflexia, bilateral ptosis with downbeat nystagmus and hypermetric

saccades. She had bilateral cerebellar signs characterised by coordination with wide-spaced ataxic gait(SARA SCALE 8: Gait-2/ Stance-1/ Sitting-0/ Speech-2/ Finger chase -1/ Tremor-0.5/ FAM-0.5/ Heel Shin-1). She also had bilateral sensorineural hearing loss, bifacial weakness and pes cavus with nerve conduction study showing absent sympathetic skin response from both lower limbs. The magnetic resonance image (MRI) of the brain showed prominent cerebellar atrophy. Her Vasculitic profile, ANA- IF, and paraneoplastic profile including GAD were negative. Whole exome & Whole Mitochondrial Genome sequencing detected a homozygous nonsense pathogenic variant (c.931C > T) in exon 6 of the ANO10 gene (chr3: g.43576923G>A;Depth:92x). This variant resulted in a stop codon and premature truncation of the protein at codon 311 (p. Gln311Ter).

Results: Peripheral neuropathy is an uncommon manifestations of SCAR10. We present a case of SCAR10 presenting with progressive cerebellar ataxia, bilateral ptosis, downbeat nystagmus, hyperreflexia and peripheral neuropathy.

Conclusion: Understanding the genotype-phenotype relationships of this rare disease will enhance patient counselling by providing better insights into disease prognosis and potential future therapeutic options.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/peripheral-neuropathy-in-autosomal-recessive-spinocerebellar-ataxia-due-to-ano10-mutation-expanding-the-phenotypic-spectrum/