Recessive loss of function mutations in MCOLN1, encoding for TRPML1, lead to mucolipidosis type IV (MLIV), a lysosomal storage disorder characterized by motor neurodegeneration, vision impairment and mental retardation, due to defective biogenesis of lipid-containing vacuoles [99,100]. The gene discussed is MCOLN1; the disease is lysosomal storage disease.