The Question
A 24-year-old man presents to the emergency department with a 5-day history of joint pain. The pain began in his right knee and has since involved his left wrist and right ankle. He also reports pain and swelling along the tendons of his left wrist. He denies any recent trauma. He has felt generally unwell with subjective fevers. He is sexually active with a new partner for the past month and reports inconsistent condom use. He denies any penile discharge, dysuria, or genital lesions. Temperature is 37.9°C (100.2°F), blood pressure is 118/72 mm Hg, pulse is 92/min, and respirations are 14/min. Physical examination reveals tenderness and swelling over the extensor carpi ulnaris tendon at the left wrist. The right knee is warm with a moderate effusion. There are several small, scattered pustules on an erythematous base on his palms and torso. A genital examination is unremarkable. Laboratory studies show a white blood cell count of 12,500/mm³ with a neutrophil predominance. Arthrocentesis of the right knee yields synovial fluid with 35,000 leukocytes/mm³ (95% neutrophils). The Gram stain of the synovial fluid is negative. Which of the following is the most appropriate next step in diagnosis?
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Post-Call Recovery Reads
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A
Explanation
Clinical Pearl:
Disseminated gonococcal infection (DGI) classically presents with the triad of tenosynovitis, dermatitis, and migratory polyarthralgia. Nucleic acid amplification testing (NAAT) from multiple mucosal sites (urogenital, pharyngeal, rectal) is the most sensitive diagnostic approach.
Explanation:
This patient's presentation of migratory polyarthralgia, tenosynovitis, and a pustular skin rash is classic for disseminated gonococcal infection (DGI). The diagnosis is confirmed by identifying *Neisseria gonorrhoeae*. However, synovial fluid and blood cultures have low sensitivity and are often negative, as is the Gram stain in this case. The highest yield diagnostic strategy, as recommended by the CDC, is to perform nucleic acid amplification testing (NAAT) on samples from all potential sites of primary mucosal infection, including the urethra, pharynx, and rectum, even in the absence of local symptoms. Therefore, obtaining these swabs is the most appropriate next diagnostic step. Requesting rheumatologic labs (ANA, RF) is inappropriate in this acute setting, where an infectious etiology is much more likely. A skin biopsy has a very low diagnostic yield for DGI. While treatment for DGI involves ceftriaxone (often with azithromycin or doxycycline to cover for chlamydia), initiating doxycycline alone is incorrect, and the immediate question is diagnostic, not therapeutic. Administering intra-articular vancomycin would target resistant gram-positive organisms like MRSA, which is not consistent with the clinical picture.
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