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 that help build bone, cartilage, tendons, corneas, skin and connective tissue.

These features may not be apparent at birth but progress as storage of GAGs affects bone, skeletal structure, connective tissues, and organs.

Neurological complications may include damage to neurons (which send and receive signals throughout the body) as well as pain and impaired motor function.

Depending on the mucopolysaccharidosis subtype, affected individuals may have normal intellect or have cognitive impairments, may experience developmental delay, or may have severe behavioral problems.

Physical symptoms generally include coarse or rough facial features (including a flat nasal bridge, thick lips, and enlarged mouth and tongue), short stature with disproportionately short trunk (dwarfism), dysplasia (abnormal bone size and/or shape) and other skeletal irregularities, thickened skin, enlarged organs such as liver (hepatomegaly) or spleen (splenomegaly), hernias, and excessive body hair growth.

In this disorder, excessive amounts of fatty materials known as lipids (another principal component of living cells) are stored, in addition to sugars.

Prenatal diagnosis using amniocentesis and chorionic villus sampling can verify if a fetus either carries a copy of the defective gene or is affected with the disorder.

Genetic counseling can help parents who have a family history of the mucopolysaccharidoses determine if they are carrying the mutated gene that causes the disorders.

Although each mucopolysaccharidosis (MPS) differs clinically, most patients generally experience a period of normal development followed by a decline in physical and/or mental function.

Hunter syndrome has two clinical subtypes and (since it shows X-linked recessive inheritance) is the only one of the mucopolysaccharidoses in which the mother alone can pass the defective gene to a son.

These include progressive dementia, aggressive behavior, hyperactivity, seizures, some deafness and loss of vision, and an inability to sleep for more than a few hours at a time.

In the syndrome's second stage, aggressive behavior, hyperactivity, profound dementia, and irregular sleep may make children difficult to manage, particularly those who retain normal physical strength.

There are four distinct types of Sanfilippo syndrome, each caused by alteration of a different enzyme needed to completely break down the heparan sulfate sugar chain.

Skeletal abnormalities include a bell-shaped chest, a flattening or curvature of the spine, shortened long bones, and dysplasia of the hips, knees, ankles, and wrists.

In its rarest form, Sly syndrome causes children to be born with hydrops fetalis, in which extreme amounts of fluid are retained in the body.

Neurological symptoms may include mild to moderate intellectual disability by age 3, communicating hydrocephalus, nerve entrapment, corneal clouding, and some loss of peripheral and night vision.

Other traits included mild facial changes, acquired short stature as seen in other MPS disorders, and normal joint movement and intelligence.

Changes to the diet will not prevent disease progression, but limiting milk, sugar, and dairy products has helped some individuals experiencing excessive mucus.

Surgery to remove tonsils and adenoids may improve breathing among affected individuals with obstructive airway disorders and sleep apnea.

[7] In May 2005, galsulfase (under the name Naglazyme), a recombinant enzyme replacement therapy also produced by Biomarin was approved for MPS VI (Marateaux-Lamy syndrome).

[8] In July 2006, the United States Food and Drug Administration approved a synthetic version of I2S produced by Shire Pharmaceuticals Group, called Elaprase, as a treatment for MPS type II (Hunter syndrome).

Vestronidase alfa (Mepsevii) is a recombinant human lysosomal beta glucuronidase for MPS VII (Sly syndrome) approved in the United States in November 2017 (Ultragenyx).