Father and son with genetically inherited MPS I

Mucopolysaccharidosis type I (MPS I) is a rare, inherited, genetic condition that can affect both children and adults, male or female. MPS I is caused by disease-causing changes in the IDUA gene. It has a wide range of symptoms
because it can affect many parts of the body and cause organ damage.

MPS I is a type of lysosomal storage disorder (LSD)

Lysosomes are round sacs found inside cells. They are filled with enzymes that break down waste materials in the body. When the lysosomes do not work properly, it leads to waste building up inside different organs. MPS I is a type of LSD.

In MPS I, the body is missing or does not have enough of an enzyme called IDUA

MPS I is caused by changes in the gene that produces an enzyme called IDUA, which works in the lysosome. Because of the changes in this gene, cells either do not have enough enzyme activity or are essentially missing it.

Deficiency of IDUA can lead to build-up of GAGs in the body

GAGs are sugars that help make bones, cartilage, skin, tendons, and other tissues in the body. Once they become older, they are taken out of the cells as waste with the help of the IDUA enzyme. As part of the normal functions, this process is always going on in the body.
In MPS I, as IDUA is deficient, GAGs accumulate in cells, which can interfere with the normal function of cells and can cause progressive damage.

Enzymes at work inside the cells, MPS I GAGs build-up due to enzyme deficiency

Mechanism of disease

GAG, glycosaminoglycan; IDUA, α-L-iduronidase; MPS I, mucopolysaccharidosis type I.