Mucolipidosis type IV is an inherited disorder that affects the development of nerves. Approximately 95% of individuals are severely affected, while the remaining 5% have a mild form of Mucolipidosis IV. Symptoms of the disease are not present at birth, but become evident by the end of the first year of life. Most infants with the disease are unable to crawl, sit up, or control hand movements. They also can have difficulty chewing and swallowing due to the muscles of the face moving too slowly. Mucolipidosis IV also affects a child's speech, vision, and ability to learn. In general, individuals with this condition are unable to develop beyond the age of 12 to 15 months. Currently, there is no cure for Mucolipidosis IV, but medical surveillance and care may help to improve some symptoms and overall condition of life. Mucolipidosis IV is expected to shorten one's lifespan, but by how much is unknown. Mucolipidosis IV is caused by pathogenic variants in the MCOLN1 gene.