ITPR1 Deletion in a Patient With Sensory Ataxic Neuropathy and Sjögren Syndrome

Sensory ataxic neuropathies (SAN) are rare large fibre sensory neuropathies characterised by progressive sensory loss and ataxia. They may be inherited or acquired. When inherited they are more commonly seen as part of a broader syndrome involving cerebellar ataxia or mitochondrial dysfunction. Isolated inherited SAN are rare, and the causes are limited, including RFC1 expansions (CANVAS), POLG variants and variants in COX20 and RNF170. Spinocerebellar ataxia type 15 (SCA15), caused by deletions in the ITPR1 gene, is another potential genetic cause of SAN, as peripheral neuropathy is commonly associated with various spinocerebellar ataxias.

A 35-year-old female who presented with an asymmetrical upper limb predominant sensory ataxic neuropathy which had initially been treated as a vasculitic neuropathy at her local hospital, underwent further evaluation.

Genetic analysis identified an approximately 6.5 Mb terminal deletion of chromosome 3p, including the ITPR1 gene.

This case report adds to the growing body of literature on ITPR1-related diseases, highlighting the phenotypic variability of ITPR1 and identifying it as a potential cause of isolated SAN. While a connection to Sjögren's syndrome cannot be excluded, the role of ITPR1 as the primary cause remains the focus. We propose that the neuropathy community consider screening SAN patients for ITPR1 deletions, as additional cases may help clarify its clinical significance.