**Question:** Mucopolysaccharidoses are caused by

A. mutations in lysosomal enzymes
B. mutations in glycosaminoglycan biosynthesis enzymes
C. mutations in extracellular matrix proteins
D. mutations in cytoskeletal proteins

**Core Concept:** Mucopolysaccharidoses are a group of inherited disorders characterized by the accumulation of mucopolysaccharides (complex carbohydrates) in lysosomes due to deficiencies in lysosomal enzymes.

**Why the Correct Answer is Right:** Mucopolysaccharidoses are caused by mutations in lysosomal enzymes (Option A). Lysosomes are organelles within cells that break down and recycle cellular waste products, including mucopolysaccharides. When these enzymes are deficient or dysfunctional, the accumulation of mucopolysaccharides leads to the characteristic clinical features of mucopolysaccharidoses.

**Why Each Wrong Option is Incorrect:**

A. Mutations in glycosaminoglycan biosynthesis enzymes (Option B) and extracellular matrix proteins (Option C) are incorrect because these enzymes and proteins are involved in the synthesis or structure of mucopolysaccharides, not their degradation.
D. Mutations in cytoskeletal proteins (Option D) are incorrect as they are involved in cell structure and movement, not the degradation of mucopolysaccharides.

**Clinical Pearl:** Mucopolysaccharidoses are a group of disorders with overlapping symptoms, making diagnosis challenging. The Happle-Richardson classification system categorizes them into seven types based on the enzyme deficiency and clinical presentation.

**Correct Answer:** A. mutations in lysosomal enzymes