What causes mucolipidoses (ML)?

Mucolipidoses are a group of genetic metabolic diseases.  In order to be affected by a ML, both parents must carry the same nonworking gene for the disease and pass on the gene in the egg and sperm.  Parents of children with mucolipidoses do not show any signs of the disease, but there are genetic tests that can determine if they are a carrier of one of the mucolipidoses conditions.

Donna Hill Howes, RN
Family Medicine

Mucolipidoses (ML) are classified as lysosomal storage diseases because they involve increased storage of substances in the lysosomes. Lysosomes are cell organelles that play a critical role in the metabolic function of our bodies. One of their primary roles is to pick up substances such as carbohydrates and lipids and break them into smaller molecules that can be used again in the metabolic process. This process is possible because lysosomes contain enzymes, which are proteins that help the body's chemistry work better and faster. Working continuously, enzymes break down carbohydrates and lipids and assist in the transfer of their byproducts throughout the rest of the cell for the production of energy or excretion.

Patients with ML are born with a genetic defect due to which their bodies either do not produce enough enzymes or, in some instances, produce ineffective forms of enzymes. Without functioning enzymes, lysosomes cannot break down carbohydrates and lipids and transport them to their normal destination. The molecules then accumulate in the cells of various tissues in the body, leading to swelling and damage of organs. In patients with ML, the molecules accumulate in the nerves, liver, muscle tissue, and the bone marrow, and cause the various symptoms associated with ML. For example, excess storage of these molecules in nerve tissues can cause mental retardation, accumulation in the tissues of the spleen and liver can cause poor functioning of these vital organs, and excess storage in the bone marrow can damage bones.

MLs are similar to another group of lysosomal storage diseases known as the mucopolysaccharidoses. While both conditions produce similar symptoms and are caused by the lack of enzymes necessary to break down and transport carbohydrates and lipids, the mucopolysaccharidoses result in an excess of sugars, known as mucopolysaccharides, in the urine. Mucopolysaccharides are not seen in the urine of patients with ML, therefore screening of the urine can help doctors distinguish between the two groups of disorders.

This answer is based on source information from National Institute of Neurological Disorders and Stroke.

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