Question:
Pseudoisomorphic phenomenon is seen in:
Pseudoisomorphic phenomenon is seen in:
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Pseudo-Koebner means auto-inoculation of an infectious agent along a scratch, as in viral warts.
Updated On: Jun 24, 2026
- Psoriasis
- Lichen planus
- Vitiligo
- Plane warts
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The Correct Option is D
Solution and Explanation
Step 1: Define the terms. The true isomorphic (Koebner) phenomenon is the appearance of typical lesions of an active skin disease along a line of trauma, seen in psoriasis, lichen planus and vitiligo.
Step 2: Define pseudoisomorphic (pseudo-Koebner) phenomenon. Here lesions also line up along a scratch, but they arise because an infectious agent is mechanically seeded into the scratched skin rather than because of a true inflammatory reaction.
Step 3: Apply to the options. Plane (flat) warts are caused by human papilloma virus; scratching spreads the virus in a linear track, producing new warts along the line. This is the classic pseudo-Koebner or pseudoisomorphic response. Molluscum contagiosum behaves the same way.
Step 4: Exclude the others. Psoriasis, lichen planus and vitiligo show the genuine Koebner phenomenon, not the pseudo form.
Conclusion: Pseudoisomorphic phenomenon is seen in plane warts. The printed key (D) is medically correct.
Step 2: Define pseudoisomorphic (pseudo-Koebner) phenomenon. Here lesions also line up along a scratch, but they arise because an infectious agent is mechanically seeded into the scratched skin rather than because of a true inflammatory reaction.
Step 3: Apply to the options. Plane (flat) warts are caused by human papilloma virus; scratching spreads the virus in a linear track, producing new warts along the line. This is the classic pseudo-Koebner or pseudoisomorphic response. Molluscum contagiosum behaves the same way.
Step 4: Exclude the others. Psoriasis, lichen planus and vitiligo show the genuine Koebner phenomenon, not the pseudo form.
Conclusion: Pseudoisomorphic phenomenon is seen in plane warts. The printed key (D) is medically correct.
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