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Mucopolysaccharidosis (MPS) VI

MPS VI is a progressive disease affecting many body systems, with debilitating manifestations including skeletal abnormalities, hearing loss, blindness, and cardiac and respiratory impairment.1,2

What is MPS VI?

MPS VI, also called Maroteaux-Lamy syndrome, is one of a group of rare, inherited, metabolic disorders known as the mucopolysaccharidoses, which have an overall prevalence of around 1 in 25,000 births.3,4 MPS diseases are lysosomal storage disorders that arise because of deficiencies in the various enzymes that break down glycosaminoglycans (GAGs), a type of carbohydrate.1 MPS VI is caused by a deficiency in the enzyme N-acetylgalactosamine-4-sulfatase (arylsulfatase B).1 The progressive accumulation of GAGs in various tissues in people with MPS VI affects many body systems and leads to serious health problems.1,2 The condition causes respiratory, cardiac, skeletal and sensory impairments, which can result in diminished functional capacity and early death.2

MPS VI is an autosomal recessive disease,1 which means that if both parents are carriers of an abnormal arylsulfatase B gene, each time they have a child there is a one in four chance of that child having MPS VI.

Symptoms of MPS VI

The symptoms of MPS VI include short stature, skeletal deformities, frequent upper-airway infections, enlarged liver and spleen, hearing loss and joint stiffness.1,2 Later in the disease, some patients may become wheelchair-bound or bedridden due to skeletal and joint problems, cardiopulmonary disease, blindness or spinal cord compression.2 MPS VI is a heterogenous disease and its symptoms, severity and progression may vary greatly from one patient to another.1,5 Some individuals have marked disease during infancy, while others have slowly progressing symptoms that develop over decades.2 Both slowly and rapidly progressing MPS VI result in a significant decline in physical and functional wellbeing, and a shortened lifespan.2

Diagnosing MPS VI3

Once suspected, MPS is usually diagnosed through biochemical or molecular testing, however, early clinical recognition of the condition is challenging because of its rarity and the varied and sometimes subtle nature of early signs and symptoms. Substantial diagnostic delays are common in MPS. The typical delay from the onset of symptoms to diagnosis is around three years (ranging from 0 to 38 years). Patients may present to an array of medical specialties, including orthopaedics, cardiology, neurology, rheumatology, paediatrics and general medicine. Diagnostic delays often involve referrals from one physician to another and place a substantial burden on the patient and caregivers. Earlier recognition allows for prompt initiation of treatment (when available) and management of secondary complications, as well as enabling families to benefit from support and counselling.

Managing MPS VI

A multidisciplinary approach is needed to manage patients with MPS VI because of the diverse spectrum of disease manifestations.1 Guidelines recommend patients should be regularly monitored so that timely interventions can be made to help avoid irreversible damage caused by the natural history of MPS VI, to manage disease manifestations and to maintain patients’ quality of life.1 This may include addressing clinical signs and symptoms through medication, surgery and physical therapy, as well as disease-modifying treatment.1,2


References
  1. Akyol MU et al. Recommendations for the management of MPS VI: systematic evidence- and consensus-based guidance. Orphanet J Rare Dis 2019;14:118.
  2. Giugliani R et al. Management guidelines for mucopolysaccharidosis VI. Pediatrics 2007;120(2):405-18.
  3. Clarke L et al. Understanding the early presentation of mucopolysaccharidoses disorders: Results of a systematic literature review and physician survey. J Inborn Errors Metab Screen 2018;6:1-12.
  4. Muenzer J. Overview of the mucopolysaccharidoses. Rheumatology (Oxford) 2011;50 Suppl 5:v4-12.
  5. NORD. Maroteaux Lamy syndrome. Available at: https://rarediseases.org/rare-diseases/maroteaux-lamy-syndrome/. Last accessed June 2021.