Mucolipidosis IV (ML4) is a neurodegenerative condition that is characterised by significant psychomotor and cognitive development delay, visual impairment, and poor muscle tone. Most reported cases have been severe, with onset in the first year of life, but some milder cases have also been seen.
If you have just received a diagnosis there is help and support available – please see ‘Further information and support’ below for links to valuable resources. It is also important to note that not every person with this condition experiences all the symptoms described and it is worth talking to your doctor or other relevant healthcare specialists to discuss you or your family member’s individual case.
Mucolipidosis IV is an autosomal recessiveRecessive disorders require both parents to carry a specific disorder-related mutation and pass it on to their child for the disorder to be inherited condition.
Of all the types of Mucolipidosis (type 1 – 4) only the ML4 form is more prevalent among Ashkenazi Jews relative to the general population.
Common signs and symptoms of Mucolipidosis IV include:
- Pronounced developmental delay in gross (e.g. sitting, standing, walking) and fine motor skills
- Marked cognitive development delay (e.g. speech)
- Visual problems including:
- Corneal clouding (onset varies from infancy to 5 years old)
- Retinal degeneration, leading to severe visual impairment and possible blindness later in life
- False appearance of crossed eyes (pseudo-strabismus)
- Sensitivity to light
- Low muscle tone (hypotonia), but tendon reflexes are usually spastic
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Mucolipidosis IV is thought to be caused by alterations in a membrane protein due to a mutation in the MCOLN1 gene leading to the blockage in the absorption of materials into the cell. As a result, complex lipids (fatty substances) accumulate within the lysosomes of cells, impairing cell function and causing the neurodegeneration characteristic of this disorder. ML4 is part of a group of ‘lysosomal storage disorders’, which all involve the harmful storage of substances in cells due to enzyme deficiencies.
There is currently no cure for Mucolipidosis IV, only treatment for the symptoms as they arise. Physical, speech and occupational therapy can be help improve the function and quality of life of affected individuals.
Children with Mucolipidosis IV typically reach a maximum developmental level of 1 to 2 years in language and motor function, although their receptive abilities are more advanced. People with ML4 typically survive to adulthood, although it is believed that life expectancy is reduced compared to healthy individuals.
Clinicians should consider a ML4 diagnosis in mildly to moderately developmentally delayed children who have corneal clouding. A diagnosis can be made via a simple blood test that checks for elevated levels of gastrin. A skin biopsy that shows characteristic storage bodies can also be used to support a diagnosis.
Genetic testing can be used to confirm a diagnosis in most people. Two particular mutations have been found to account for over 95% of cases of ML4 among Ashkenazi Jews. Carrier testing and prenatal testing are also available for ML4.
For more details about testing, please refer to the testing section.
This UK-based charity represents people affected by a mucopolysaccharide or related lysosomal storage disease, including ML4. The Society’s include: providing information about the diseases, offering a range of support services, and promoting and supporting research.
Phone: 0845 389 9901
The ML4 Foundation is USA-based non-profit organisation that funds, promotes, and supports medical research dedicated to developing effective treatments and cures for ML4. The site provides information, discussion forums and links to news and resources relating to ML4.
A Facebook Group supported by the ML4 Foundation.
To find out more about general resources relevant to Jewish genetic disorders, please visit our resources and support section.