## **Core Concept**
Zellweger syndrome is a rare, congenital disorder characterized by the absence or near-absence of **peroxisomes** in the cells of the body. Peroxisomes are organelles responsible for the breakdown of fatty acids and amino acids. The disorder leads to severe neurological, hepatic, and other systemic abnormalities.

## **Why the Correct Answer is Right**
The correct answer, **D. Peroxisomal biogenesis disorder**, is right because Zellweger syndrome is indeed caused by mutations in the **PEX** genes, which are essential for peroxisome biogenesis. This results in the inability to properly assemble peroxisomes, leading to the accumulation of very-long-chain fatty acids (VLCFAs) and other substances that are normally broken down within these organelles.

## **Why Each Wrong Option is Incorrect**
- **Option A: Mitochondrial disorder** - While mitochondrial disorders can present with similar symptoms due to the critical role of mitochondria in energy production, Zellweger syndrome specifically involves peroxisomal dysfunction, not mitochondrial.
- **Option B: Lysosomal storage disease** - Lysosomal storage diseases result from defects in lysosomal function, leading to accumulation of substrates. Although Zellweger syndrome involves accumulation of substances, it is primarily due to peroxisomal dysfunction, not lysosomal.
- **Option C: Golgi apparatus disorder** - The Golgi apparatus is involved in protein modification and transport. Disorders affecting the Golgi apparatus have different pathologies and are not associated with the biochemical abnormalities seen in Zellweger syndrome.

## **Clinical Pearl / High-Yield Fact**
A key clinical feature of Zellweger syndrome is the presence of **high levels of very-long-chain fatty acids (VLCFAs)** in the blood, which is a diagnostic hallmark. This results from the inability of peroxisomes to break down VLCFAs. Clinicians should consider Zellweger syndrome in infants with severe neurological impairment, hepatomegaly, and characteristic facial features.

## **Correct Answer: D. Peroxisomal biogenesis disorder**