Is this asymptomatic eruption acne - or something else?

Case 3:
For 10 days, a 42-year-old woman has had this asymptomatic eruption on her trunk and proximal extremities. She is otherwise healthy.

What is your clinical impression?

A. Acne vulgaris.
B. Rosacea.
C. Pityrosporum folliculitis.
D. Gram-negative folliculitis.
E. Grover disease.

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A culture grew Pseudomonas aeruginosa, which confirmed the diagnosis of gram-negative folliculitis, D. The patient denied any exposure to a hot tub. What is the next question you would ask this patient?

After she was asked about her bathing habits, the patient said she used the same shower net sponge every day to apply liquid cleanser. She threw out the sponge, scrubbed down the shower with bleach, received a 1-week course of ciprofloxacin, and did not have a recurrence.

Acne vulgaris would be unlikely to occur as an acute eruption in an adult with no history of acne. Rosacea typically involves the face. Pityrosporum folliculitis resembles Pseudomonas folliculitis and needs to be differentiated by culture. Grover disease is characterized by slightly crusted, erythematous, pruritic papules.