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Diseases Studied

The Rare Diseases Clinical Research Network is an NIH-funded research network of 20 active consortia or research groups working to advance treatment for diseases that are rare. Use the search tools on this page to find the diseases we currently study. You can reach out to the indicated consortia or research groups for more information on those diseases and studies underway.

This network focuses on clinical research and does not generally support clinical care outside of research activities. To learn about other rare diseases, please visit the Genetic and Rare Diseases Information Center (GARD), which is an NIH program that helps the public find reliable information about rare and genetic diseases. Their staff are specialists. Contact them at 1-888-205-2311 or email

All Diseases > Hunter Syndrome

Hunter Syndrome (MPS II)

Alternative Names: Mucopolysaccharidosis Type II; Iduronate 2-Sulfatase Deficiency (I2S Deficiency)

Disease Category: Lysosomal Diseases

A rare, X-linked recessive (requiring two gene mutations found on the X chromosome - one from each parent), inherited, lysosomal disorder, caused by a missing or abnormal enzyme which cannot break down glycosaminoglycans (GAGs, complex sugar molecules with amino groups that are critical components of connective tissues). The 2 subtypes, non-neuronopathic (mild form not affecting neurons) and neuronopathic (severe form affecting neurons), manifest in early childhood, affecting the respiratory airway, eyes, ears, liver, spleen, and the skeletal, neurological, and cardiac systems.

Research groups studying this disease

Lysosomal Diseases
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Lysosomal Disease Network (LDN)

Serves as a voice for children and adults with Hunter syndrome (mucopolysaccharidosis or MPS II), working to find a cure through research and advocacy.