Mucopolysaccharidosis type 2

Mucopolysaccharidosis type 2 (MPS II), also known as Hunter syndrome, is a rare lysosomal storage disorder caused by deficiency of the enzyme iduronate-2-sulfatase (IDS). This enzyme is essential for the breakdown of glycosaminoglycans (GAGs), specifically dermatan sulfate and heparan sulfate. When these complex sugar molecules cannot be properly degraded, they accumulate progressively in cells and tissues throughout the body, leading to widespread organ damage. MPS II presents along a clinical spectrum ranging from a severe (neuronopathic) form to an attenuated (non-neuronopathic) form. The severe form, which accounts for approximately two-thirds of cases, typically manifests between ages 2 and 4 with coarse facial features, skeletal abnormalities (dysostosis multiplex), joint stiffness, hepatosplenomegaly (enlarged liver and spleen), recurrent ear and respiratory infections, hearing loss, cardiac valve disease, and progressive intellectual disability. Children with the severe form often experience behavioral disturbances and progressive neurological decline, with life expectancy typically into the second decade. The attenuated form shares many of the somatic features but spares the central nervous system, allowing normal or near-normal intelligence, with patients potentially surviving into adulthood. Because MPS II is X-linked recessive, it predominantly affects males, though rare symptomatic female carriers have been reported. Treatment options include enzyme replacement therapy (ERT) with idursulfase (Elaprase), which was approved in 2006 and can improve some somatic symptoms such as walking capacity, respiratory function, and organ size, though it does not cross the blood-brain barrier effectively and therefore has limited impact on neurological disease. Hematopoietic stem cell transplantation (HSCT) has been explored but its role remains less established compared to other MPS types. Intrathecal ERT and gene therapy approaches are under active investigation to address the neurological component of the disease. Supportive and multidisciplinary care, including management of airway, cardiac, orthopedic, and hearing complications, remains a cornerstone of treatment.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Mucopolysaccharidosis type 2