Differences in MPS I and MPS II Disease Manifestations

Area of Science:

• Biochemistry
• Genetics
• Cell Biology

Background:

• Mucopolysaccharidosis (MPS) types I and II are lysosomal storage diseases caused by deficiencies in specific enzymes involved in glycosaminoglycan catabolism.
• MPS II results from iduronate 2-sulfatase (IDS) deficiency, blocking heparan sulfate (HS) and dermatan sulfate (DS) degradation.
• MPS I stems from iduronidase (IDUA) deficiency, affecting a later step in DS degradation.

Purpose of the Study:

• To elucidate the biochemical basis for phenotypic differences between MPS I and MPS II.
• To understand how varying HS and DS levels influence disease-specific manifestations.
• To inform the development of targeted therapies for central nervous system (CNS) involvement.

Main Methods:

• Comparative analysis of glycosaminoglycan (HS and DS) ratios and sulfation levels in MPS I and MPS II.
• Correlation of biochemical findings with clinical phenotypes, including skeletal, corneal, epidermal, and neurological manifestations.
• Review of current and experimental therapeutic strategies, focusing on enzyme replacement therapy (ERT) and CNS-targeted approaches.

Main Results:

• MPS I exhibits higher DS/HS ratios and lower sulfation levels, correlating with corneal clouding.
• MPS II shows dominant HS levels and higher sulfation, linked to epidermal manifestations and potentially neurological involvement.
• Accumulation of HS and DS leads to cellular dysfunction, impacting lysosomes and various cellular processes.

Conclusions:

• Distinct glycosaminoglycan profiles in MPS I and II underlie their specific clinical presentations.
• Understanding these differences is crucial for developing effective treatments, particularly for CNS manifestations.
• Experimental therapies focusing on delivering IDS to the CNS are critical for addressing neurocognitive decline in MPS II.