Question

NARP syndrome is seen in which type of disorder?

• A. Mitochondrial function disorder
• B. Glycogen storage disorder
• C. Lysosomal storage disorder
• D. Lipid storage disorder

Hint:

Neuropathy, Ataxia, Retinitis Pigmentosa from an MT-ATP6 mutation points to one organelle.

Answer 1

The Correct Option is A

Step 1: NARP stands for Neuropathy, Ataxia and Retinitis Pigmentosa.
Step 2: NARP is caused by a point mutation in mitochondrial DNA, classically the m.8993T>G mutation in the MT-ATP6 gene, which encodes a subunit of mitochondrial ATP synthase (complex V) of the oxidative phosphorylation chain.
Step 3: Because the defect lies in mitochondrial DNA and impairs ATP production, NARP is a mitochondrial (oxidative phosphorylation) disorder and shows maternal inheritance.
Step 4: A high mutant load of the same m.8993 mutation produces the more severe maternally inherited Leigh syndrome, underscoring its mitochondrial basis.
Step 5: The other categories are unrelated: glycogen storage disorders (for example Pompe, von Gierke), lysosomal storage disorders (for example Gaucher, Tay-Sachs) and lipid storage disorders involve enzyme deficiencies in different pathways and do not cause NARP.
Conclusion: The correct answer is mitochondrial function disorder.