46-year-old man presents with linear rash on left side of chest
How long have you had this rash? How quickly did it develop?
When I took a shower on Friday night, I didn't see anything. The next morning it was there and it has spread since then.
Good question for the start; a feel for the onset and acuity of the disease will help with diagnosis and therapy.
Were you recently in a public swimming pool?
Yes, I go swimming twice a week in a public outdoor pool.
What are you looking for? This question doesn't help.
Has anyone in your family died of cancer?
This question not only doesn't help; it also makes the patient worried.
Did you have pain or burning in the area before the skin changes appeared?
Yes, a day before I started noticing a tugging pain.
Very good question; this dermatosis is often preceded by prodromal pain or burning.
Did you have chickenpox as a kid?
I don't think so. At least no one ever told me so.
Good question. The patient must have had chickenpox. Either the infection was subclinical or the history is wrong.
Have you ever had an HIV test?
Good question, as the patient is somewhat young for this illness and it is definitely associated with immunosuppression.
Have you every had anything like this before?
Good question. This disease only recurs in the face of immunosuppression.
Choose the right efflorescences:
A keratosis features a focal thickening of the stratum corneum. This is not seen here.
Vesicles are small fluid-filled lesions; here we see multiple grouped vesicles. Some lesions are clear; others, cloudy.
This dermatosis may scar, but so far, no scars are seen.
Atrophy means a loss of substance of the skin; this has not occurred here.
Choose the right diagnosis:
Epidermolysis bullosa is a congenital disease with increased skin fragility. This is not the story here.
Tinea versicolor is a chronic fungal infection with hyper- or hypopigmented, scaly patches. No sign of that here.
Impetigo can start with vesicles and pustules but rapidly crusts. In addition, a dermatomal distribution and grouped small lesions are both unlikely.
Gooda classic diagnosis! A dermatomal vesicular disease with a prodrome in an adult is herpes zoster.
Choose the right therapy(ies):
Bland drying therapy may be all that is needed.
Theoretically useful, but too expensive and ineffective over wide areas.
This is not a bacterial disease. Topical disinfectants suffice to help avoid bacterial secondary infection.
There is no advantage to this approach and topical corticosteroids might even delay healing.
Possible indications include: age > 50 years, marked pain, immunosuppression, involvement of 1st, 2nd branches of trigeminal nerve. Ideally should be started within 72 hours.