Steroid-Induced Acne Fluorinated

A 28-year-old male bodybuilder presents with a 3-week history of an acneiform eruption over his chest, back, and shoulders. On examination, the lesions marked **A** in the diagram are noted—small, uniform, erythematous papules all at the same stage of evolution. He admits to self-administering intramuscular testosterone and nandrolone for the past 6 weeks. Which clinical feature of the lesions marked **A** is most characteristic of steroid-induced acne and helps distinguish it from acne vulgaris?