Enzyme deficiency in Hunter disease is:
**Core Concept**
Hunter disease, also known as mucopolysaccharidosis type II (MPS II), is a genetic disorder caused by the deficiency of the lysosomal enzyme iduronate-2-sulfatase (I2S). This enzyme is crucial for the breakdown and recycling of sugar molecules in the body.
**Why the Correct Answer is Right**
The deficiency of iduronate-2-sulfatase leads to the accumulation of dermatan sulfate and heparan sulfate in various tissues, resulting in cellular damage and organ dysfunction. The enzyme plays a vital role in the degradation of glycosaminoglycans (GAGs), which are essential components of connective tissue. The accumulation of GAGs due to I2S deficiency causes the characteristic features of Hunter disease, including clouded corneas, progressive neurological deterioration, and skeletal abnormalities.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the enzyme deficiency in Hunter disease is not related to alpha-L-iduronidase (the enzyme deficient in Hurler syndrome, another type of mucopolysaccharidosis).
**Option B:** This option is incorrect because the enzyme deficiency in Hunter disease is not related to beta-glucuronidase (an enzyme involved in the breakdown of glycosaminoglycans but not the primary enzyme deficient in Hunter disease).
**Option C:** This option is incorrect because the enzyme deficiency in Hunter disease is not related to arylsulfatase B (an enzyme involved in the breakdown of sulfated glycolipids but not the primary enzyme deficient in Hunter disease).
**Clinical Pearl / High-Yield Fact**
It is essential to differentiate Hunter disease from other mucopolysaccharidoses, as the enzyme deficiencies can lead to distinct clinical presentations. A key differentiating feature of Hunter disease is the preservation of motor function, which distinguishes it from Hurler syndrome (MPS I), where motor function is often impaired.
**Correct Answer:** C. iduronate-2-sulfatase (I2S)