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Mucolipidosis IV
Sunday, 08 August 2004
Sunday, 08 August 2004
Sailolipidosis

What

Mucolipidosis IV is a rare, inherited, lysosomal storage disease that most commonly occurs in children of Jewish descent. A lysosome is the part of the cell that is responsible for breaking down digested nutrients like fats and carbohydrates into simpler substances to be used by the cell. To do this, the lysosome uses special proteins called enzymes. In lysosomal storage diseases, such as Mucolipidosis IV, one of these enzymes is missing or not working correctly. This results in an accumulation of fats (mucolipids) and complex carbohydrates within the cells of many tissues of the body. This build-up of material causes progressive damage to virtually every cell of the body.

Who

Mucolipidosis IV is very rare with approximately 80 diagnoses made to date. This disease most commonly occurs in Jewish people of Ashkenazi decent. Exactly how often this disease occurs is unknown. It is estimated that 1 out of every 100 Ashkenazi Jews is a carrier for the defective gene that causes Mucolipidosis IV.

Signs and Symptoms

Mucolipidosis IV most often appears in the first year of life with the following symptoms: 1. Developmental delays in gross motor skills such as sitting, standing and walking. 2. Developmental delays in fine motor skills such as holding a crayon or spoon. 3. Developmental delays in speech. 4. Vision problems including: a. Corneal clouding (Clouding of the clear part of the eye through which light passes) b. Retinal degeneration (degeneration of the nerve rich membrane lining the eyes. This can lead to blindness) c. Sensitivity to light d. Strabismus (crossed eyes) 5. Low muscle tone 6. Mental retardation

Possible Causes

Mucolipidosis IV is caused by a defect in a gene named MCOLN 1 and this gene is located on chromosome 19. This gene produces a protein named mucolipin. Children with Mucolipidosis IV do not make enough normal mucolipin. It is thought that mucolipin plays a role in moving calcium through cellular membranes; however the exact function of mucolipin and how it relates to the function of the lysosomes must still be determined. Mucolipidosis IV is inherited in an autosomal recessive manner. This means that both parents must carry an abnormal copy of the gene and both parents must pass this changed (mutated) copy to the child. There is a 1 in 4 chance (25%) in each pregnancy of having an affected child if both parents carry a changed copy of this gene. Carriers themselves do not have the disease because they still have one normal copy of the gene.

Diagnosis

A diagnosis of Mucolipidosis IV should be considered in children who display the above described signs and symptoms, especially if they are of Ashkenazi Jewish background. Examining cells with an electron microscope can confirm the diagnosis by revealing the characteristic accumulation of fat and carbohydrates (storage bodies) in almost every cell of the body. It is now possible to offer genetic carrier testing and prenatal diagnosis for Mucolipidosis IV, both for families with a previous history of the disease and for all couples of Ashkenazi Jewish ancestry. The carrier screening test requires a sample of blood and can determine whether or not there is a gene mutation present for Mucolipidosis Type IV. Prenatal diagnosis can be done with the use of CVS (Chorionic Villus Sampling) or Amniocentesis, which are performed early in the pregnancy.

Treatment

Unfortunately, there is no cure for Mucolipidosis IV. Supportive care can, however, significantly improve the function and quality of life of affected children. Supportive care can include physical, occupational and speech therapy. Evaluation and continuous care by an ophthalmologist (eye doctor) is recommended early to detect and treat any eye problems. Special education can help children attain their fullest potential at school.

Prognosis

The long-term outcome and life expectancy for children with Mucolipidosis IV is unknown. Mildly affected children have been identified, raising the possibility of undiagnosed individuals living a relatively healthy and normal lifespan. Affected children typically reach a maximum developmental age of 15 months in language and motor function

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

ML4 Foundation
Support network for families of children diagnosed with mucolipidosis type 4.

Mucolipidosis IV connections: E-mail Pal List
Email list of parents and professionals interested in talking with others about Mucolipidosis IV. Live chat room and Q & A links.

National Foundation for Jewish Genetic Diseases
Provides an overview of Mucolipidosis IV and other diseases affecting Jewish populations. Also contains screening information and other resources for parents.

Google Search for Mucolipidosis IV

References and Sources

1. OMIM: Mucolipidosis IV www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=252650 2. www.mazornet.com/genetics/ML4.asp 3.Raas-Rothschild (May June ’99) Mucolipidosis type 4: The origin of the disease in the Ashkenazi Jewish population, Eur J. Hum Genet. 7(4):496-498