Because a complex of UBXD1-p97 is required for recruitment of ubiquitylated caveolin-1 to the lysosome for degradation this pathway becomes impaired in the disease mutants, leading to the accumulation of caveolin-1 positive endolysosomes in IBMPFD patients (Ritz et al., 2011). This evidence concerns the gene VCP and inclusion body myopathy with Paget disease of bone and frontotemporal dementia.