What is mucopolysaccharidosis?
What is mucopolysaccharidosis?
Briefly: Mucopolysaccharidosises are a group of metabolic disorders caused by the absence or malfunctioning of lysosomal enzymes (caused by a genetic mutation) needed to break down molecules called glycosaminoglycans (formerly called mucopolysaccharides). Over time, these glycosaminoglycans (GAGs) accumulate in the cells, blood and connective tissues and progressively damage those as well as causing enlarged liver spleen and skin thickening. As a consequence the condition of the patients are progressively deteriorate, nearly all of their organs are damaged and most of them do not survive adult age.
The human body contains connective tissues (cartilage, tendons and skin), which forms together with the bones a solid frame (skeleton) and a cover (skin). The main component of the connective tissues are the GAGs, which are long chains of sugar carbohydrates. In normal cases the GAGs are break down in the lysosomes by enzymes, which are highly specialized proteins essential for survival. Lysosomal disorders like mucopolysaccharidosis are triggered when a particular enzyme exists in too small amount or it is missing altogether.
Currently, there are 6 different types of MPS disease, each of them is defined by a different enzyme defect:
- MPS I. Hurler, Scheie
- MPS II. Hunter
- MPS III. Sanfilippo
- MPS IV. Morquio
- MPS VI. Maroteaux-Lamy
- MPS VII. Sly
The above listed MPS types are very similar in respect their symptoms and progress of the disease, while the total number of cases is less than a hundred in Hungary and in abroad have similar proportions. Therefore, we have to deal with all these diseases in one association, and with some even more rare diseases, which appear in low number in Europe called: lysosomal metabolic disease (Mucolipidosis, Mannosidosis, Fucosidosis etc.).
In Hungary currently only few laboratories are able to diagnose this type of diseases and unfortunately they can only perform the simplest tests. In order to determine the exact type, enzyme and molecular genetic analyses are needed. Currently the closest institute available for such tests are only in Graz and Hamburg. Although, if the family would like to have a second child, they need to know the exact diagnosis of the already born child. To diagnose the disease based on only the symptoms is not reliable as sometimes the signs do not clearly define the type. Furthermore parents also have the right to know what to expect, because at distinct types the life outlook can be different.
Treatment and therapy
The disease is incurable, according to the current state of research. The treatment is mostly palliative which can alleviate some symptoms but do not stop the progressive nature of the disease. The medical experience indispensable in order to decide what therapy is feasible, which does not cause unnecessary suffering and financial difficulties for the patients and parents. Unfortunately the bone marrow transplantation did not meet the high expectations, however at certain types in early onset the symptoms can be alleviated. Currently the most accepted treatment is the ERT (enzyme replacement therapy) which has its limitations as do not cure neural symptoms. There are several Hungarian MPS I and MPS II patients receiving ERT.
About the disease types
You can find further information on the different MPS types on the following website: (http://mpssociety.org/)