Clinical studies in 82 individuals with valosin-containing protein (VCP) associated multisystem proteinopathy and literature review.

Valosin-containing protein (VCP) pathogenic variants cause a multisystem proteinopathy characterized by myopathy, Paget disease of bone, frontotemporal dementia, and amyotrophic lateral sclerosis (ALS). We evaluated 82 affected individuals, 14 presymptomatic carriers, and 36 unaffected first-degree relatives from 48 families to identify sensitive measures for disease monitoring. Mean age of onset was ∼42 years for myopathy, Paget disease, or ALS, and 53 years for dementia. Functional assessments included the Inclusion Body Myositis Functional Rating Scale (IBMFRS), ALSFRS-R, Fatigue Severity Scale (FSS), and six-minute walk test (6MWT). Affected individuals demonstrated progressive functional decline, with IBMFRS decreasing 1.9% annually, FSS increasing 4.4%, and 6MWT decreasing 6% annually when modeled against disease duration. Women declined more rapidly on IBMFRS but showed slower ambulatory and fatigue progression. Potential genotype-specific effects were observed, with earlier onset and shorter survival in p.Arg155Cys compared to later onset in p.Arg155His. Strong correlations among IBMFRS, FSS, and 6MWT indicate these as accessible endpoints for longitudinal monitoring and clinical trials. Rapid decline with ALS and dementia necessitates multidisciplinary support, while longer survival after myopathy or Paget onset offers a window for preventive and supportive interventions.