Mucopolysaccharidosis VI (MPS VI, Maroteaux-Lamy syndrome)

Mucopolysaccharidosis VI has an estimated incidence ranging from 1:248,000 to 1:1,300,000 in different geographical areas. It is an autosomal recessive lysosomal storage disorder due to arylsulfatase B (ARSB) deficiency, leading to systemic accumulation of the glycosaminoglycan (GAG) dermatan sulfate (Figure 1).

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Figure 1. Anatomy and morphometry of the olfactory epithelium (OE) in MPS-affected and control cats. (A) In the nasal septum of affected MPS VI animals, lysosomal storage is evident in chondrocytes, based on the presence of abundant clear vacuoles in the cytoplasm (asterisks). (B) In control animals, chondrocytes in the septum show no evidence of lysosomal storage.
[Taken from Lischka FW, Gomez G, Yee KK, Dankulich-Nagrudny L, Lo L, Haskins ME, Rawson NE (2008). Altered olfactory epithelial structure and function in feline models of mucopolysaccharidoses I and IV. J Comp Neurol 511: 360-372].

MPS VI clinical phenotype is heterogeneous and is characterized by onset usually around 6-24 months of age, progressive development of coarse facial features, macrocephaly, skeletal deformities, joint stiffness, progressive clouding of the cornea, glaucoma, growth retardation, hearing loss, heart valve thickening and possible cardiomyopathy, inguinal and umbilical hernias, and hepatosplenomegaly.

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Courtesy of MPS VI.com

Figure 2. Altered Stance of MPS VI. A 30-year-old male with marked manifestations of MPS VI exhibits a flexed-knee, crouched stance typical of the disease. This altered stance reflects reduced joint mobility and widespread skeletal abnormalities.

MPS VI is generally not associated with mental progressive impairment, although some complications such as communicating hydrocephalus can be associated with neurological clinical signs, and physical disabilities. Death, usually resulting from respiratory infections or cardiac disease, may occur between the second and the fourth decade, depending on phenotype severity.

Due to its rarity, limited information is available in the literature concerning the natural history of MPS VI. To date no available treatment for MPS VI is able to completely reverse its clinical phenotype. Bone marrow transplantation can be considered as a possible therapeutic option for selected patients with a severe phenotype. ERT with recombinant human ARSB (rhARSB) has been recently introduced but requires further post-marketing studies. Also, it requires weekly infusions, with a significant impact on patients’ life style and quality of life, and has very high costs. Therefore further studies should be performed to develop alternative therapeutic approaches with higher efficacy and less significant impact on both patients’ quality of life and health system pharmacoeconomic policies.

Learn more at:
Wikipedia

Patient organizations:
Mucopolysaccharidosis VI – WrongDiagnosis.com
Associazione Italiana Mucopolisaccaridosi