Genetic Spectrum and Phenotypic Variability in Chinese Patients with Multisystem Proteinopathy and Related Disorders.

OBJECTIVE: Multisystem proteinopathy (MSP) is a pleiotropic group of disorders initially presenting as inclusion body myopathy (IBM), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and/or Paget disease of bone (PDB). Additional genes including METHODS: Twenty-nine patients were identified in 953 patients diagnosed with ALS, IBM, or dementia at Huashan Hospital between 2000 and 2024. Variants in MSP-related genes were detected using next-generation sequencing and confirmed by Sanger sequencing. Clinical, pathological, imaging, and electromyography data were collected and analyzed. RESULTS: A total of 29 patients (3.0%) were identified as carrying MSP-related gene variants. Most patients were male (72.4%), with disease onset predominantly in the third to fifth decades of life. The majority of patients (21/29) presented with a single clinical phenotype. ALS was the most common phenotype (20/29), followed by IBM (10/29), FTD (7/29), and PDB (1/29). The most frequent variants were in CONCLUSION: This study broadens the clinical and genetic landscape of MSP and related disorders in a Chinese cohort. These results emphasize the clinical utility of next-generation sequencing for improving diagnostic accuracy in patients with unexplained neuromuscular or cognitive presentations, especially in the presence of multisystem involvement.