Mucolipidosis IV (MLIV) is a progressive neurological lysosomal storage disease that usually is evident during the first year of life, and presents with mental retardation, corneal opacities, and delayed developmental milestones. Ocular findings also include retinal degeneration, myopia, strabismus, and photophobia. Neurological symptoms include hypotonia and pyramidal tract signs. There are cytoplasmic inclusions (“storage bodies”) in almost every cell type of the patients. Most affected individuals reach a maximal developmental age of 12-15 months. Mucolipidosis IV is due to mutations in the MCOLN1 gene and more than 80% of reported patients are of Ashkenazi Jewish descent. Two common mutations (IVS3-2 A>G and a 6,450bp deletion) account for 95% of cases in the Ashkenazi Jewish population. MLIV is rare in the general population.