Question

In Hurler syndrome, which glycosaminoglycans accumulate and cause organ enlargement?

• A. Keratan sulfate and dermatan sulfate
• B. Keratan sulfate and heparan sulfate
• C. Heparan sulfate and dermatan sulfate
• D. Keratan sulfate and hyaluronic acid

Hint:

Hurler syndrome = alpha-L-iduronidase deficiency = accumulation of heparan sulfate and dermatan sulfate.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the specific metabolic byproducts (glycosaminoglycans or GAGs) that build up in Hurler syndrome (Mucopolysaccharidosis Type I).
Step 2: Detailed Explanation:

Overview of Hurler Syndrome: It is an autosomal recessive lysosomal storage disorder caused by the deficiency of the enzyme Alpha-L-iduronidase.

Biochemical Block: Alpha-L-iduronidase is required to break down certain GAGs. When it is missing, these substances accumulate in the lysosomes of various tissues, including the liver, spleen, heart, and brain.

Specific GAGs: The specific substrates for this enzyme are Heparan sulfate and Dermatan sulfate. Their accumulation is responsible for the systemic manifestations of the disease.

Clinical Signs: The build-up causes coarse facial features (gargoylism), hepatosplenomegaly (organ enlargement), corneal clouding, and skeletal deformities.

Comparison with Hunter Syndrome: Hunter syndrome (MPS II) also involves the accumulation of Heparan and Dermatan sulfate, but it is X-linked and notably lacks corneal clouding.

Analyzing Options: Only Option C correctly identifies the pair of GAGs specific to MPS I and MPS II. Keratan sulfate (found in other options) is associated with Morquio syndrome (MPS IV).

Step 3: Final Answer:
The deficiency of alpha-L-iduronidase in Hurler syndrome leads to the pathological accumulation of Heparan sulfate and Dermatan sulfate.