Feline Mucopolysaccharidoses (MPSs) – NAVLE Study Guide

Overview and Clinical Importance

Mucopolysaccharidoses (MPSs) are a group of inherited lysosomal storage diseases caused by deficiencies of enzymes required for the degradation of glycosaminoglycans (GAGs). These complex carbohydrates, including dermatan sulfate, heparan sulfate, and chondroitin sulfate, accumulate within lysosomes when enzyme activity is deficient or absent, leading to progressive cellular dysfunction and multisystemic disease.

In cats, three types of MPS have been well-documented: MPS I (Hurler syndrome equivalent), MPS VI (Maroteaux-Lamy syndrome equivalent), and MPS VII (Sly syndrome equivalent). MPS VI is the most common form in felines and has been extensively studied in Siamese cats. These disorders are inherited as autosomal recessive traits, meaning both parents must carry the defective gene for offspring to be affected.

Pathophysiology

Mechanism of Disease

GAGs are essential components of connective tissue extracellular matrix, cartilage, and the cornea. The stepwise degradation of GAGs requires multiple lysosomal enzymes. In MPS, deficiency of a specific enzyme causes accumulation of partially degraded GAGs within lysosomes, leading to: