Biomarker for Mucolipidosis Disorder Type I, II, III, IV AN INTERNATIONAL, MULTICENTER, EPIDEMIOLOGICAL PROTOCOL

Mucolipidoses (ML) are a group of inherited metabolic diseases in which both glycosaminoglycans (GAGs) and another group of substances called sphingolipids build up in the body. GAGs are long, repeating chains of complex sugar molecules, and sphingolipids are fats. ML disorders may also be referred to as "targeting defects" because affected individuals are lacking the enzyme (a protein that produces chemical reactions in the body) that "targets" other enzymes to the lysosome (a sac-like structure found in a cell).

Symptoms of ML can be congenital (present at birth) or begin in early childhood or adolescence. Early symptoms can include vision problems and developmental delays. Over time, many children with ML develop poor mental capacities, have difficulty reaching normal developmental milestones, and, in many cases, eventually die of the disease.

Changes in specific genes results in the deficiency or absence of the targeting enzyme. The ML disorders are categorized into four groups based on the clinical features and enzyme deficiencies. ML-II and ML-III are the more common forms of ML. An individual is usually suspected of having an ML disorder based on clinical features. The diagnosis is further confirmed by laboratory testing.

The mucolipidoses are inherited in an autosomal recessive manner, that is, they occur only when a child inherits two copies of the defective gene, one from each parent. When both parents carry a defective gene, each of their children faces a one in four chance of developing one of the MLs. At the same time, each child also faces a one in two chance of inheriting only one copy of the defective gene. People who have only one defective gene are known as carriers. These individuals do not develop the disease but they can pass the defective gene on to their own children. Because the defective genes involved in certain forms of ML are known, tests can identify people who are carriers in some instances.

The four types of ML are Sialidosis (sometimes referred to as ML I), and types II, III, and IV.