MPS I and MPS II share many features. It can therefore be difficult to make an accurate diagnosis based on clinical presentation alone.1 Clinical presentation in combination with the appropriate diagnostic tests ensures diagnosis of the correct MPS subtype.  

A diagnosis of MPS I or MPS II is based on quantitative testing of GAG concentration in urine and enzyme activity in tissue.1 The urinary GAG (UGAG) assay is the initial diagnostic step when an MPS disorder is suspected. A positive UGAG result is followed up by measurement of enzyme activity to confirm diagnosis.

When there is a family history of MPS I or MPS II, UGAG screening should be bypassed and an enzyme assay be performed as the first diagnostic step.2

In this section, learn more about the tests used to diagnose MPS I and MPS II.


  1. 1.Lehman TJ, Miller N, Norquist B, Underhill L, Keutzer J. (2011) Diagnosis of the mucopolysaccharidoses. Rheumatology (Oxford) 50 Suppl 5: v41-48.
  1. 2.Burton BK, Giugliani R. (2012) Diagnosing Hunter syndrome in pediatric practice: practical considerations and common pitfalls. Eur J Pediatr 171(4): 631-639.