The loss-of-function mutations in TRPML1 directly cause the lysosomal storage disorder mucolipidosis type IV (MLIV), a neurodegenerative disease characterized by abnormal neurodevelopment, retinal degeneration, and iron-deficiency anemia (Bargal et al., 2000; Bassi et al., 2000; Gan and Jiang, 2022; Nilius et al., 2007). This evidence concerns the gene MCOLN1 and mucolipidosis type IV.