Like many components of the body, proteoglycans need to be broken down and replaced. When the body breaks down proteoglycans, one of the resulting products is mucopolysaccharides (GAGs).In MPS II, the problem concerns the breakdown of two GAGs: dermatan sulfate and heparan sulfate. The first step in the breakdown of dermatan sulfate and heparan sulfate requires the lysosomal enzyme iduronate-2-sulfatase, or I2S. In people with MPS II, this enzyme is either partially or completely inactive. As a result, GAGs build up in cells throughout the body, particularly in tissues that contain large amounts of dermatan sulfate and heparan sulfate. The rate of GAGs buildup is not the same for all people with MPS II, resulting in a wide spectrum of medical problems. Diagnosis
The first laboratory screening test for an MPS disorder is a urine test for GAGs. Abnormal values indicate that an MPS disorder is likely. The urine test can occasionally be normal even if the child actually has an MPS disorder. A definitive diagnosis of MPS II is made by measuring I2S activity in serum, white blood cells, or fibroblasts from skin biopsy. In some people with MPS II, analysis of the I2S gene can determine clinical severity.Prenatal diagnosis is routinely available by measuring I2S enzymatic activity in amniotic fluid or in chorionic villus tissue. If a specific mutation is known to run in the family, prenatal molecular genetic testing can be performed. DNA sequencing can reveal if someone is a carrier for the disease.
Treatment
Because of the wide variety of phenotypes, the treatment for this disorder is specifically determined for each patient. Until recently,  no effective therapy for MPS II was available, so palliative care was used. Recent advances, though,  have led to medications that can improve survival and well-being in people with MPS II. Enzyme replacement therapy
Idursulfase, a purified form of the missing lysosomal enzyme, underwent clinical trial in 2006 and was subsequently approved by the United States Food and Drug Administration as an enzyme replacement treatment for MPS II. Idursulfase beta, another enzyme replacement treatment, was approved in Korea by the Ministry of Food and Drug Safety. Recent advances in enzyme replacement therapy (ERT) with idursulfase have been proven to improve many signs and symptoms of MPS II, especially if started early in the disease. After administration, it can be transported into cells to break down GAGs, but as the medication cannot cross the blood–brain barrier, it is not expected to lead to cognitive improvement in patients with severe central nervous system symptoms. Even with ERT, treatment of various organ problems from a wide variety of medical specialists is necessary. Bone-marrow and stem-cell transplantation
Bone-marrow transplantation and hematopoietic stem-cell transplantation (HSCT) have been used as treatments in some studies. While transplantation has provided benefits for many organ systems, it has not been shown to improve the neurological symptoms of the disease. Although HSCT has shown promise in the treatment of other MPS disorders, its results have been unsatisfactory so far in the treatment of MPS II.