Atypical — MCQs

Question 1: A 27-year-old man comes to the physician with throbbing right scrotal pain for 1 day. He has also had a burning sensation on urination during the last 4 days. He is sexually active with multiple female partners and does not use condoms. Physical examination shows a tender, palpable swelling on the upper pole of the right testicle; lifting the testicle relieves the pain. A Gram stain of urethral secretions shows numerous polymorphonuclear leukocytes but no organisms. Which of the following is the most likely causal pathogen of this patient's symptoms?

• A. Mycobacterium tuberculosis
• B. Pseudomonas aeruginosa
• C. Mumps virus
• D. Chlamydia trachomatis (Correct Answer)
• E. Staphylococcus aureus

Explanation: ***Chlamydia trachomatis*** - The patient's presentation with **epididymitis** (scrotal pain, tender palpable swelling on the upper pole of the testicle), **dysuria**, and a history of **multiple sexual partners without condoms** is classic for a sexually transmitted infection. - **Positive Prehn's sign** (pain relief with testicular elevation) supports epididymitis over testicular torsion. - The Gram stain showing **numerous polymorphonuclear leukocytes but no organisms** is highly suggestive of *C. trachomatis* infection, as it is an **obligate intracellular bacterium** that does not readily stain with Gram stain. - This finding distinguishes it from *Neisseria gonorrhoeae* (the other common cause of STI-related epididymitis in young men), which would appear as **Gram-negative intracellular diplococci**. *Mycobacterium tuberculosis* - **Tuberculosis epididymitis** is rare in developed countries and typically presents with a more **insidious onset** over weeks to months, not acute onset over 1 day. - It may involve caseating granulomas and is more common in immunocompromised patients. - It would not explain the acute dysuria or the Gram stain findings of PMNs without organisms in a patient with risk factors for common STIs. *Pseudomonas aeruginosa* - **Pseudomonas epididymitis** is typically seen in older men (>35 years), those with urinary tract abnormalities, or after instrumentation/catheterization. - It is uncommon in young, sexually active individuals without these risk factors. - Gram stain would show **Gram-negative rods**, which is inconsistent with the "no organisms" finding. *Mumps virus* - **Mumps orchitis** typically presents with **testicular pain and swelling** (affecting the testis itself, not the epididymis). - Mumps orchitis is usually preceded by **parotitis** (salivary gland swelling) 4-8 days earlier. - It does not typically cause dysuria or lead to urethral secretions with PMNs. - Mumps is now rare due to widespread MMR vaccination. *Staphylococcus aureus* - **Staphylococcus aureus** can cause epididymitis, especially in cases of direct trauma, hematogenous spread, or in patients with indwelling catheters. - However, it's not a common cause of sexually transmitted epididymitis in young, healthy men. - A Gram stain would reveal **Gram-positive cocci in clusters**, which was not seen in this case.