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 t ...

s that affect the body's ability to carry out the normal turnover of various materials within

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

s. When originally named, the mucolipidoses derived their name from the similarity in presentation to both

mucopolysaccharidoses Mucopolysaccharidoses are a group of metabolic disorders caused by the absence or malfunctioning of lysosomal enzymes needed to break down molecules called glycosaminoglycans (GAGs). These long chains of sugar carbohydrates occur within the cells ...

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 Glycoproteinosis are lysosomal storage diseases affecting glycoproteins, resulting from defects in lysosomal function. The term is sometimes reserved for conditions involving degradation of glycoproteins. Types * (E77.0) Defects in post-translat ...

, 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 chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, ...

s target carbohydrate residues on N-linked glycoproteins. Without this phosphorylation, the glycoproteins are not destined for

lysosomes A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane prote ...

, 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 autosom ...

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 an ...

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.

Diagnosis

The

diagnosis Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine "cause and effect". In systems engin ...

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. Laboratory services are provided in a variety of settings: physi ...

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 result of mucolipidosis.

Treatment

There is currently no known treatment or specific therapy to cure this disease. However, there are multiple therapy techniques that 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 and vitamin B12 may also be required if the patient needs them.

References

External links