INF2-Related Charcot–Marie–Tooth Disease in a Japanese Cohort: Genetic and Clinical Insights

Background: INF2 mutations cause focal segmental glomerulosclerosis (FSGS) and Charcot–Marie–Tooth disease (CMT). Accurate genetic diagnosis is critical, as INF2-related FSGS is typically resistant to immunotherapy yet rarely recurs after transplantation, and its associated neuropathy can mimic treatable immune-mediated disorders such as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).<br> Methods: We performed a multicenter study investigating 3329 Japanese patients with inherited peripheral neuropathies/CMT who underwent gene panel sequencing or whole-exome analysis between 2007 and 2024. Clinical data, including electrophysiological assessments, were obtained from the patients' medical records.<br> Results: We identified six pathogenic INF2 variants in eight patients, all of which were located within the diaphanous inhibitory domain. Structural modeling revealed clustering of variants near the diaphanous autoregulatory domain-binding pocket, which is critical for INF2 autoinhibition. Clinically, all cases were sporadic, with a median age at neurological onset of 9 years. All patients exhibited lower limb weakness, and 6/8 (75%) had sensory disturbances. All patients also developed kidney dysfunction, with 7/8 (88%) progressing to end-stage renal disease at a median age of 15 years. Furthermore, all patients showed demyelinating neuropathy, and 2/8 (25%) received immunotherapy due to suspected immune-mediated neuropathy.<br> Conclusion: Although INF2 variants are a rare cause of CMT in Japan, they should be considered in pediatric patients with demyelinating neuropathy and early-onset proteinuria, even in the absence of a family history. Blood and urine tests assessing renal dysfunction can provide guidance for appropriate genetic testing.