Work

Mutation in RNF170 causes sensory ataxic neuropathy with vestibular areflexia: a CANVAS mimic

Year: 2020

Type: article

Abstract: Sensory neuronopathy or ganglionopathy is a type of peripheral neuropathy characterised by primary and selective destruction of the dorsal root ganglia leading to degeneration of both central and peripheral neurites of sensory neurons.1 There is a narrow differential diagnosis for a sensory ganglionopathy which includes paraneoplastic (anti-Hu antibodies), autoimmune (Sjogren syndrome,), toxic (cisplatin, pyridoxine) and genetic (Friedreich’s ataxia and mitochondrial disease due to POLG1 mutations) causes.2 More recently biallelic AAGGG expansion in replication factor complex subunit 1 have been identified as a major cause of sensory ataxia neuropathy, often with cerebellar and vestibular involvement (CANVAS).3 4 However, a significant fraction of patients with a sensory ganglionopathy remain genetically undiagnosed. In 2004 Valdamanis et al identified a heterozygous p.Arg199Cys mutation in ring finger protein 170 ( RNF170 ) responsible for a rare form of sensory ataxia in two families from eastern Canada sharing a founder haplotype.5–7 Affected cases showed progressive sensory loss and ataxia due to degeneration of the posterior columns, but normal sensory nerve conduction. By exome-sequencing we have identified the same p.Arg199Cys RNF170 mutation in an Ecuadorian family affected by an autosomal dominant late-onset progressive sensory ganglionopathy. Unlike the previously reported cases from Eastern Canada, affected members showed evidence of ganglionic/postganglionic involvement of the sensory peripheral nerves. Also, bilateral vestibular areflexia was identified in the index case, mimicking CANVAS. The index case (III-3, figure 1A) is a 57-year-old woman with onset of poor balance at the age of 47 years, followed by dysaesthesia and sensory loss in her feet and hands. At the age of 57 years she was referred for neurological evaluation, by which time she required a walking aid. Her past medical history was notable for rheumatic fever and gastro-oesophageal reflux. A sister had similar symptoms and her father and paternal grandmother both reported progressive …

Source: Journal of Neurology Neurosurgery & Psychiatry

DOI: 10.1136/jnnp-2020-323719