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Storage diseases

Mucopolysaccharidoses (MPS) are a group of rare inherited progressive diseases which have a range of clinical features, often multisystem and with a range of severity. 

  • The clinical features are due to a genetic defect resulting in reduced or absent lysosomal enzyme activity which break down glycosaminoglycans (GAGs). The end result is abnormal tissues in bone, cartilage, tendons, corneas, skin, and connective tissue.
  • The genetic defects are known for many MPS conditions: most are autosomal recessives and therefore cases are more common in consanguineous families. 
  • Enzyme replacement therapy is available for some MPS conditions and can prevent or at least slow down the progression of the diseases. Bone Marrow transplantation is an option for some of the more severe MPS conditions. 
  • Clinical features vary across the different MPS types and there is a wide range of clinical features even within MPS types with grades of severity ranging from early death in the most severe cases through to an almost normal clinical phenotype. Clinical features include: 
    • Short stature, joint symptoms (swelling, contractures, carpal tunnel syndrome) or joint deformity and sometimes joint excessive laxity occur.
    • Bone dysplasia, trunk limb disproportions and facial dysmorphism occur.
    • Cardiorespiratory abnormalities can be severe and are a major cause of morbidity and mortality.
    • Hepatosplenomegaly, corneal clouding and cataracts reflect the multisystem nature of the diseases
    • There can be progressive developmental regression.
  • Diagnosis rests on clinical suspicion, urine testings for GAGs and ultimately blood testing for lysosomal enzymes. 

More information about the diagnosis of MPS is available.

A video demonstration of joint examination in a child with MPS is available.

Further information about considering MPS in the context of joint contractures is available on pmm.



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