Iduronate 2-sulfatase deficiency

A genetic disorder affecting the breakdown of glycosaminoglycans

Iduronate 2-sulfatase deficiency
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Synonyms	Hunter syndrome, MPS II
Pronounce	N/A
Specialty	N/A
Symptoms	Developmental delay, skeletal abnormalities, organomegaly
Complications	N/A
Onset	Childhood
Duration	Lifelong
Types	N/A
Causes	Genetic mutation in the IDS gene
Risks	N/A
Diagnosis	Genetic testing, clinical evaluation
Differential diagnosis	N/A
Prevention	N/A
Treatment	Enzyme replacement therapy, supportive care
Medication	N/A
Prognosis	Variable, depending on severity
Frequency	Rare
Deaths	N/A

Iduronate 2-sulfatase deficiency, also known as Hunter syndrome or Mucopolysaccharidosis type II (MPS II), is a rare genetic disorder that affects the body's ability to break down certain complex molecules known as glycosaminoglycans (GAGs). This condition is caused by mutations in the IDS gene, which encodes the enzyme iduronate 2-sulfatase. This enzyme is essential for the degradation of GAGs, specifically dermatan sulfate and heparan sulfate.

Pathophysiology

In individuals with iduronate 2-sulfatase deficiency, the lack of functional enzyme leads to the accumulation of GAGs in various tissues and organs. This accumulation causes progressive damage and dysfunction, particularly affecting the skeletal system, cardiovascular system, respiratory system, and central nervous system. The severity of the disease can vary widely among affected individuals, ranging from mild to severe forms.

Clinical Presentation

Symptoms of iduronate 2-sulfatase deficiency typically appear in early childhood. Common clinical features include:

• Developmental delay and cognitive impairment
• Distinctive facial features, often described as "coarse"
• Enlarged liver and spleen (hepatosplenomegaly)
• Joint stiffness and skeletal abnormalities
• Hearing loss
• Respiratory difficulties

Diagnosis

Diagnosis of iduronate 2-sulfatase deficiency is based on clinical evaluation, biochemical tests, and genetic testing. Measurement of enzyme activity in leukocytes or fibroblasts can confirm the deficiency of iduronate 2-sulfatase. Genetic testing can identify mutations in the IDS gene, providing a definitive diagnosis.

Treatment

Currently, there is no cure for iduronate 2-sulfatase deficiency. Treatment focuses on managing symptoms and improving quality of life. Enzyme replacement therapy (ERT) with recombinant iduronate 2-sulfatase (idursulfase) is available and can help reduce GAG accumulation and alleviate some symptoms. Supportive care, including physical therapy, occupational therapy, and surgical interventions, may be necessary to address specific complications.

Prognosis

The prognosis for individuals with iduronate 2-sulfatase deficiency varies depending on the severity of the condition. Early diagnosis and intervention can improve outcomes, but the disease is progressive and can lead to significant morbidity and reduced life expectancy, particularly in severe cases.

Also see

• Mucopolysaccharidosis
• Lysosomal storage disease
• Genetic disorder
• Enzyme replacement therapy