A 43-year-old businessman visits his primary care physician complaining of a purulent penile discharge. He had unprotected sex with a woman he met at a conference 1 week ago. Gram stain of the discharge fails to reveal any organisms. Which of the following is the most likely cause of the discharge?: (A) Bowen disease, (B) Chlamydia trachomatis, (C) Herpes simplex virus, (D) Treponema pallidum
Answer is B. C. trachomatis is one of the leading causes of urethritis and should be suspected whenever a gonorrhea-like discharge fails to show gram-negative diplococci within neutrophilic phagocytes. It is a sexually transmitted disease that can also cause epididymitis. Bowen disease presents as a single erythematous plaque on the penis or scrotum and may evolve into invasive carcinoma. Herpes simplex virus can cause a vesicular rash on the penis. T. pallidum causes syphilis, which may present with a painless chancre on the penis.