Question

A 28 year old patient has multiple grouped papulovesicular lesions on both elbows, knees, buttocks and upper back associated with severe itching. The most likely diagnosis is:

• A. Pemphigus vulgaris
• B. Bullous pemphigoid
• C. Dermatitis Herpetiformis
• D. Herpes zoster

Hint:

Extensor surfaces plus buttocks plus intense itch is the classic Dermatitis Herpetiformis pattern.

Answer 1

The Correct Option is C

This question is testing whether you can separate the major blistering skin diseases by their favorite body sites and how itchy they are.

1. Pemphigus vulgaris: Gives soft, fragile blisters that break easily, usually starting in the mouth before spreading to the trunk. Itching is mild, so the severe itch here argues against it.
2. Bullous pemphigoid: Gives firm, tense blisters, mostly in older adults, often over the trunk and flexural folds rather than a symmetric elbow, knee, buttock, and back pattern.
3. Dermatitis Herpetiformis: Gives small grouped blisters and papules with intense itching, and it has a strong preference for extensor surfaces, elbows, knees, buttocks, and the upper back, which is exactly the pattern described.
4. Herpes zoster: Gives grouped vesicles too, but always along a single nerve root on one side of the body, with pain rather than a widespread symmetric rash over multiple joints and the back.

The site pattern (elbows, knees, buttocks, upper back) combined with severe itching is the signature of Dermatitis Herpetiformis, so that is the answer.

Let's summarize:

• Extensor surface plus buttock involvement with severe itch favors Dermatitis Herpetiformis.
• A single dermatome pattern would point to zoster instead, which is not seen here.

So the most likely diagnosis is Dermatitis Herpetiformis.