Fibroblasts from mucolipidosis type IV patients exhibit enlarged vacuoles with accumulated lipids and acid mucopolysacharides, suggesting the role for TRPML1 in trafficking of proteins and lipids (Riedel et al., 1985; Goldin et al., 1999; Slaugenhaupt et al., 1999). This evidence concerns the gene MCOLN1 and mucolipidosis type IV.