Mucolipidosis Type IV (ML4) is a progressive disease that results in growth and developmental delays, progressive visual impairment caused by clouding of the cornea and retinal degeneration, and features that are sometimes misdiagnosed as cerebral palsy.
Some children with ML4 may learn to sit or crawl, however most never walk without assistance, and the majority do not learn to speak. Other symptoms may include difficulties with chewing and swallowing. Most individuals with ML4 survive into adulthood, although the overall lifespan is thought to be shortened. The most severe form of this condition is typically found in people with Ashkenazi Jewish ancestry.
There is no cure for ML4. Currently, treatments for ML4 are limited to managing the symptoms.
About 1 in 100 to 1 in 127 Ashkenazi Jewish individuals is a carrier for Mucolipidosis Type IV.
How Is Mucolipidosis Type IV Inherited?
The cells in our body typically contain 46 chromosomes. Each chromosome is a package that holds hundreds of genes. These genes contain the all of the blueprints for our growth and development; they are the instructions that make us who we are. All of our chromosomes (and the genes that are located on these chromosomes) come in pairs. We inherit one chromosome of each pair from our mother and the other chromosome of the pair from our father.
;)
When there is a change in a gene (called a mutation) the instructions it contains are no longer correct and the gene cannot carry out its function. Individuals with ML4 have two copies of a mutation, one copy inherited from each parent. Neither gene in the pair is working correctly, which causes the symptoms of the disease.
A carrier of ML4 is a person who has a mutation in one gene of the pair. Carriers are unaffected with the disease because the properly working gene is able to compensate for the gene that contains the mutation.
When two parents are carriers of ML4:
- there is a 1 in 4 (25%) chance of having a child with ML4,
- there is a 1 in 2 (50%) chance of having a child who is an unaffected carrier like the parents,
- and, there is 1 in 4 (25%) chance of having a child who is unaffected and is not carrier.
When one parent is a carrier of ML4 and the other parent is not a carrier, they are not at increased risk to have a child with ML4. Instead, there is a 1 in 2 (50%) chance of having a child with is an unaffected carrier like the one parent.
What This Test Tells You
This test tells whether you are a carrier of ML4. It looks for the two mutations that account for >95% of mutations that cause ML4 in people of Ashkenazi Jewish descent. These mutations are called IVS3-2A>G and 511>6944del in the MCOLN1 gene.
How Testing Works
Testing with DNA Direct is quick, convenient, and can be done in the privacy of your home. It can also be anonymous if you wish. How to order online and consult with our genetic experts: DNA Direct's Expert Services
References:
1. Sun M, Goldin E, Stahl S. et al. Mucolipidosis type IV is caused by mutations in a gene encoding a novel transient receptor potential channel. Hum Mol Gen. 2000; 9(17):2471-2478.2. American college of obstetricians and gynecologists. Prenatal and preconceptional carrier screening for genetic diseases in individuals of eastern european jewish descent. Technical Bulletin 298. Washington, DC: ACOG. August, 2004.
3. Slaugenhaupt S. The molecular basis of mucolipidosis type IV. Curr Mol Med. 2002; 2(5):445-450.
4. Edelmann L, Dong J, Desnick RJ, Kornreich R. 2002. Carrier screening for mucolipidosis type IV in the American Ashkenazi Jewish population. Am J Hum Genet 70:1023-1027.
5. Bargal R, Avidan N, Ben-Asher E et al. 2000. Identification of the gene causing mucolipidosis type IV. Nat Genet 26:118-123.
