# A novel KIDINS220 mutation associated with hereditary spastic paraplegia accompanied by severe peripheral neuropathy

## TL;DR

A new mutation in the KIDINS220 gene is linked to hereditary spastic paraplegia and severe peripheral neuropathy in a Chinese family.

## Contribution

A novel KIDINS220 mutation in the SAM domain is identified, expanding the clinical and genetic spectrum of KIDINS220-related disorders.

## Key findings

- The mutation c.3668A > G (p. Glu1223Gly) in the SAM domain of KIDINS220 was found in a family with HSP and severe peripheral neuropathy.
- Nerve biopsy showed myelin defects, axonal degeneration, and mitochondrial abnormalities in the proband.
- Literature review confirmed the mutation expands the known clinical and genetic features of KIDINS220-related disorders.

## Abstract

Mutations in KIDINS220 are known to cause hereditary spastic paraplegia (HSP) and SINO syndrome. However, the phenotypic and genotypic spectrum of KIDINS220-related disorders remains incompletely understood. Herein, we describe the clinical, electrophysiological, histopathological, and genetic features of a novel KIDINS220 sterile alpha motif (SAM) -like domain mutation identified in a Chinese family with HSP accompanied by severe peripheral neuropathy (PN).

Clinical data, electrophysiological characteristics, and sural nerve histopathology were analyzed in a 19-year-old Chinese male. Genetic testing was performed in his family by using whole-exome sequencing, mitochondrial genome testing, and Sanger validation. A comprehensive literature review was conducted to analyze the phenotypic and genetic data of previously reported cases with KIDINS220 variants up to July 2025.

The proband exhibited classical signs of autosomal dominant HSP accompanied by severe multifocal sensory-motor PN. The spinal cord MRI showed mild spinal cord thinning, while the brain MRI and nerve ultrasound examinations were normal. Electrophysiological study revealed absent sensory nerve responses and globally reduced motor conduction velocities. Sural nerve biopsy confirmed significantly reduced nerve fiber density, myelin defects, axonal degeneration, and mitochondrial abnormalities. A heterozygous KIDINS220 c.3668A > G (p. Glu1223Gly) mutation, located within the SAM domain, was identified in both the proband and his mother. A total of 42 cases from 11 cohorts were reviewed.

We suggest that patients with KIDINS220 SAM domain mutation may present with HSP accompanied by severe, mixed axonal and demyelinating PN, expanding the existing spectrum of the clinical phenotypes and pathogenic variants of KIDINS220.