Orf (ecthyma contagiosum) is a zoonotic viral infection caused by parapoxvirus, contracted from sheep or goats. The pathognomonic clinical evolution occurs in 6 stages. The characteristic stage 2 lesion is:
- A A weeping nodule with haemorrhagic crust
- B A flat target-like lesion with red centre, white ring and red halo ✓
- C A painless verrucous plaque
- D Umbilicated vesicles in a dermatomal distribution
Correct answer: B. A flat target-like lesion with red centre, white ring and red halo
Explanation
Orf progresses through 6 classic stages: (1) maculopapular, (2) target stage (flat target lesion with red centre, white ring, red halo—pathognomonic), (3) acute weeping stage, (4) nodular stage, (5) papillomatous stage, (6) regressive stage. Each stage lasts approximately 1 week, giving total duration of ~6 weeks. The target lesion in stage 2 is the hallmark of orf. Immunity is not permanent, reinfection can occur. Lesions are usually solitary on hands in farmers/abattoir workers.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.