Mucopolysaccharidosis type 6, slowly progressing

Mucopolysaccharidosis type 6 (MPS VI), also known as Maroteaux-Lamy syndrome, is a rare lysosomal storage disorder caused by deficiency of the enzyme arylsulfatase B (N-acetylgalactosamine-4-sulfatase, encoded by the ARSB gene). This enzyme is responsible for breaking down the glycosaminoglycan (GAG) dermatan sulfate. When the enzyme is deficient, dermatan sulfate accumulates in cells and tissues throughout the body, leading to progressive multi-organ damage. The slowly progressing form of MPS VI represents the attenuated end of the clinical spectrum, with later onset and milder disease progression compared to the rapidly progressing form. In the slowly progressing form, symptoms typically emerge in later childhood or adolescence and progress more gradually. Key clinical features include joint stiffness and contractures, mild to moderate skeletal abnormalities (dysostosis multiplex), corneal clouding leading to visual impairment, mild coarsening of facial features, and cardiac valve disease. Unlike the rapidly progressing form, patients with the slowly progressing phenotype generally have normal or near-normal height, preserved cognitive function, and longer survival. However, cardiac valve involvement, carpal tunnel syndrome, and skeletal complications can still cause significant morbidity over time. Enzyme replacement therapy (ERT) with galsulfase (Naglazyme) is the primary treatment for MPS VI and has been shown to improve endurance, pulmonary function, and joint mobility. Hematopoietic stem cell transplantation (HSCT) has also been used in some cases. Supportive care is essential and may include orthopedic interventions, cardiac monitoring and surgery, ophthalmologic management, and physical therapy. Early diagnosis and treatment initiation are important to slow disease progression and improve quality of life, even in the attenuated form.

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