What Is Mucolipidosis IV?
Mucolipidosis IV is an inherited lysosomal storage disorder caused by mutations in the MCOLN1 gene. Individuals with mucolipidosis IV lack an enzyme called mucolipin-1, which is important for the proper functioning of lysosomes, the digestive system of the cell, though its exact function is not fully understood.
Mucolipidosis IV affects the development of the nerves. In about 15% of cases, it also causes existing nerves to degenerate. Most infants with the condition are unable to sit up, crawl, or control their hand motions. They also chew and swallow very slowly, because the muscles of their mouth and face move slowly or not at all. Children with the condition never learn to walk independently, although a few have learned to use a walker. When they are able to speak, they tend to do so either very slowly or very quickly and slur words, mumble, or whisper. In addition, they rarely learn more than a few words, although some children with mucolipidosis IV have learned to communicate with a few dozen basic signs. In general, individuals with the disease only reach a developmental age of 12 to 15 months.
Mucolipidosis IV leads to poor vision caused by cloudy corneas (the clear front part of the eye) and degeneration of the retina (the part inside the eye which translates light into images). Individuals with the disease are also prone to dry, irritated eyes, crossed eyes, and pupils that respond slowly to changes in light levels. Although infants with the condition may be born with nearly normal vision, their vision almost always starts to deteriorate by the age of five. Almost everyone with the condition has severe visual impairments by their early teens.
About 5% of individuals with the condition have an atypical variation with less-severe movement and vision problems.
How Common Is Mucolipidosis IV?
Fewer than 100 cases of mucolipidosis IV have been reported in medical literature, and the incidence of mucolipidosis IV in the general population is unknown. Approximately 70 to 80% of those affected are of Ashkenazi Jewish background, where the incidence is 1 in 32,000.
How Is Mucolipidosis IV Treated?
Treatment for mucolipidosis IV focuses on ensuring comfort and improving function. Physical therapy, foot and ankle orthotics, walkers, and wheelchairs can help maximize mobility. Speech therapy may improve the ability to communicate. Younger children frequently develop eye irritation, which lubricating eye drops, gels, or ointments can soothe.
What Is the Prognosis for an Individual with Mucolipidosis IV?
Mucolipidosis IV typically shortens one's lifespan, but individuals with the disease commonly reach adulthood and some are known to be alive in their mid-forties.