Question

A 56 year old man has painful rashes over his right upper eyelid and forehead for the last 48 hours. He underwent chemotherapy for Non-Hodgkin's lymphoma one year ago. His temperature is 98 degree F, blood pressure 138/76 mm Hg, and pulse is 80/minute. Examination shows no other abnormalities. Which of the following is the most likely diagnosis?

• A. Impetigo
• B. Herpes zoster
• C. Pyoderma gangrenosum
• D. Erysipelas

Hint:

Painful rash along the V1 dermatome in an immunocompromised patient points to shingles.

Answer 1

The Correct Option is B

Step 1: Note the pattern of the rash.
The pain and rash are confined to the right upper eyelid and forehead, an area supplied by the ophthalmic division (V1) of the trigeminal nerve. A rash that respects one nerve's territory and stops at the midline is called a dermatomal rash.

Step 2: Note the timeline and risk factors.
The rash appeared only 48 hours ago and is painful, and pain often comes before or with the rash in this condition. The man had chemotherapy for Non-Hodgkin's lymphoma a year back, and chemotherapy weakens cell-mediated immunity for a long time afterward, which is exactly the kind of immune weakness that lets a dormant virus reactivate.

Step 3: Connect the findings to the diagnosis.
Herpes zoster (shingles) happens when the varicella-zoster virus, which stays dormant in a sensory ganglion after childhood chickenpox, reactivates and travels down one sensory nerve. A painful, dermatomal rash in an immunocompromised patient is the textbook picture of herpes zoster, and when it involves V1 it is called herpes zoster ophthalmicus, which needs urgent attention because it can affect the eye itself.

Step 4: Rule out the other options.

(1) Impetigo: A superficial bacterial skin infection with honey-colored crusts, it does not follow a nerve's path and is not typically this painful.

(3) Pyoderma gangrenosum: Causes deep, ulcerating lesions, usually on the legs, and is linked to inflammatory bowel disease or blood disorders, not a dermatomal distribution.

(4) Erysipelas: A bacterial skin infection with a sharply raised, red, warm plaque, usually with fever and systemic illness, which this patient does not have (temperature is normal).

Final Answer:
A painful, dermatomal rash on the forehead and eyelid in an immunocompromised patient is herpes zoster.
\[ \boxed{\text{Herpes zoster}} \]