Mucolipidosis is a group of inherited

metabolic disorder A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients, such as proteins, fats, and carbohydrates. Metabolic disorders can happen when abnormal chemical reactions in the body alter the ...

s that affect the body's ability to carry out the normal turnover of various materials within cells. When originally named, the mucolipidoses derived their name from the similarity in presentation to both mucopolysaccharidoses and sphingolipidoses. A biochemical understanding of these conditions has changed how they are classified. Four conditions (types I, II, III, and IV) were historically labeled as mucolipidoses. However, type I ( sialidosis) is now classified as a glycoproteinosis, and type IV ( Mucolipidosis type IV) is now classified as a gangliosidosis.

ML II and III

The other two types are closely related. Mucolipidosis types II and III (ML II and ML III) result from a deficiency of the enzyme N-acetylglucosamine-1-phosphotransferase, which

phosphorylate In biochemistry, phosphorylation is described as the "transfer of a phosphate group" from a donor to an acceptor. A common phosphorylating agent (phosphate donor) is ATP and a common family of acceptor are alcohols: : This equation can be writt ...

s target carbohydrate residues on N-linked

glycoproteins Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...

. Without this phosphorylation, the glycoproteins are not destined for lysosomes, and they escape outside the cell.

Genetics

The mucolipidoses are inherited in an

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosome ...

recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and ...

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 children. Because the defective genes involved in certain forms of ML are known, tests can identify people who are carriers in some instances.

Diagnosis

The

diagnosis Diagnosis (: diagnoses) is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in a lot of different academic discipline, disciplines, with variations in the use of logic, analytics, and experience, to determine " ...

of ML is based on clinical symptoms, a complete medical history, and certain

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as schools ...

tests. Symptoms of the disease are usually present at birth or begin in early childhood. Early symptoms can include skeletal abnormalities, vision problems, and developmental delays. Poor mental capacities and difficulty reaching physical developmental milestones may also be the result of mucolipidosis.

Treatment

There is currently no known treatment or specific therapy to cure this disease. However, multiple therapies can be used to help with some of the symptoms. Speech therapy and physical therapy may aid in a diagnosed child's motor and speech delays. Nutritional supplements such as

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

and

vitamin B12 Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. One of eight B vitamins, it serves as a vital cofactor (biochemistry), cofactor in DNA synthesis and both fatty acid metabolism, fatty acid and amino a ...

may also be required if the patient needs them.

References

External links