Inclusion body myopathy with Paget disease of bone and frontotemporal dementia (IBMPFD), also known as VCP disease and multisystem proteinopathy (MPS I), is an autosomal dominant hereditary disorder caused by monoallelic variants in the valosin containing protein (VCP) gene on chromosome 9p13.3–12. The gene discussed is VCP; the disease is inclusion body myopathy with Paget disease of bone and frontotemporal dementia.