Which of the following lysosomal storage disorders is characterized by accumulation of heparan sulfate and dermatan sulfate due to deficiency of multiple sulfatases?

Explanation

## Multiple Sulfatase Deficiency — A Rare Lysosomal Disorder **Key Point:** Multiple sulfatase deficiency (MSD) is a rare autosomal recessive lysosomal storage disorder caused by deficiency of a **post-translational modification enzyme** (SUMF1 gene product) required to activate ALL sulfatases. This results in simultaneous deficiency of multiple sulfatases and accumulation of multiple sulfated substrates, including **heparan sulfate** and **dermatan sulfate**. ### Pathophysiology 1. SUMF1 enzyme normally converts a cysteine residue in sulfatases to formylglycine (FG), which is essential for catalytic activity 2. Without SUMF1, all sulfatases become inactive 3. Multiple substrates accumulate: - Heparan sulfate (normally degraded by heparan sulfate sulfatase) - Dermatan sulfate (normally degraded by dermatan sulfate sulfatase) - Sulfatide (normally degraded by arylsulfatase A) - Steryl sulfate (normally degraded by steroid sulfatase) ### Distinction from Individual Sulfatase Deficiencies | Disorder | Enzyme Deficiency | Substrates Accumulated | CNS Involvement | |----------|-------------------|------------------------|------------------| | **Multiple Sulfatase Deficiency** | SUMF1 (activator) | Heparan sulfate, dermatan sulfate, sulfatide, steryl sulfate | Severe; infantile-onset | | **MPS I (Hurler)** | α-L-iduronidase | Heparan sulfate, dermatan sulfate | Moderate–severe | | **MPS II (Hunter)** | Iduronate-2-sulfatase | Heparan sulfate, dermatan sulfate | Mild–severe (X-linked) | | **MPS VII (Sly)** | β-Glucuronidase | Heparan sulfate, dermatan sulfate, chondroitin sulfate | Mild–moderate | | **Metachromatic Leukodystrophy** | Arylsulfatase A | Sulfatide only | Severe; progressive | **High-Yield:** Multiple sulfatase deficiency is the ONLY disorder where a defect in a **post-translational modification enzyme** (not the sulfatases themselves) causes multiple sulfatase inactivity. This is a classic NEET PG trap question. ### Clinical Features - Infantile-onset (usually <6 months) - Severe developmental regression - Seizures, spasticity, blindness - Hepatosplenomegaly - Skeletal dysplasia - Death typically by age 3–5 years **Clinical Pearl:** The key distinguishing feature is that MSD presents with a combination of features seen in multiple individual MPS disorders simultaneously, because multiple sulfatases are deficient at once. **Mnemonic:** **SUMF1 = Sulfatase Modification Factor 1** — remember that MSD is a defect in the *modifier*, not the *modified*. [cite:Robbins 10e Ch 5]