TRPML1 mutation increases the formation of autophagosomes, disrupts the fusion of autophagosomes and lysosomes, and induces the accumulation of p62 and insufficient removal of ubiquitinated proteins and/or defective mitochondria in fibroblasts from patients with mucolipidosis type IV (MLIV; Vergarajauregui et al., 2008; Nakamura et al., 2020). This evidence concerns the gene MCOLN1 and mucolipidosis type IV.