Xeroderma pigmentosum (XP) results from a defect in nucleotide excision repair. Which specific XP complementation group is associated with the most severe neurological involvement (De Sanctis-Cacchione syndrome)?
- A XP-A ✓
- B XP-C
- C XP-V
- D XP-D
Correct answer: A. XP-A
Explanation
XP complementation group A (XP-A) shows the most severe clinical phenotype including De Sanctis-Cacchione syndrome (XP with severe neurological degeneration — progressive microcephaly, choreoathetosis, cognitive impairment). XP-A has almost no nucleotide excision repair activity. XP-C is the most common form but has mild/no neurological disease. XP-V (variant) is due to defective translesion synthesis polymerase eta, not NER itself. XP-D overlaps with Cockayne syndrome.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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