MCOLN1 and mucolipidosis type IV: Mucolipidosis type IV (MLIV), an ultra-rare lysosomal storage disease (LSD) primarily found in the Ashkenazi Jewish population [1], is caused by mutations in the MCOLN1 gene, which encodes the late endosomal/lysosomal transient receptor potential channel TRPML1 (mucolipin 1) [2].