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Difficulty: MediumFormulating a Differential Diagnosis

A 26-year-old woman comes to the urgent care clinic due to a 4-day history of joint pain and a new rash. The pain initially involved her left elbow and right wrist but currently affects her right ankle, making it difficult to walk. She also reports intermittent subjective fevers over the same period. Her medical history is unremarkable, and she takes an oral contraceptive. She has been sexually active with a new male partner for the past two months. Her temperature is 38.2°C (100.8°F), blood pressure is 110/70 mm Hg, and pulse is 98/min. Physical examination reveals swelling, warmth, and marked tenderness along the dorsum of the right wrist and over the left Achilles tendon. There is no significant joint effusion in the knees or ankles. Auscultation of the heart reveals a grade 1/6 early systolic murmur at the left lower sternal border. Skin examination shows a few sparse, discrete necrotic pustules on an erythematous base located on the distal upper and lower extremities. Pelvic examination reveals no cervical motion tenderness or vaginal discharge. Which of the following is the most likely diagnosis?

  1. Disseminated gonococcal infectionAnswer
  2. B
    Reactive arthritis
  3. C
    Infective endocarditis
  4. D
    Secondary syphilis
  5. E
    Adult-onset Still disease

Answer

Disseminated gonococcal infection
The correct answer is Disseminated gonococcal infection. This condition frequently affects young, sexually active individuals, particularly women, who may have an asymptomatic primary mucosal infection (as evidenced by this patient's normal pelvic exam). The systemic spread of Neisseria gonorrhoeae typically results in a classic clinical triad: migratory polyarthralgia, tenosynovitis (inflammation of the tendon sheath, commonly affecting the wrists, fingers, ankles, and toes), and dermatitis (typically characterized by sparse, discrete necrotic pustules or vesiculopustules on the distal extremities). The presence of this complete triad makes it the most likely diagnosis.

Step-by-Step Solution

1
Analyze the patient's demographic risk factors and vital signs.
The patient is a young, sexually active female with a new partner, presenting with an acute febrile illness (temperature 38.2°C).
Identifying systemic inflammation in the context of recent sexual exposure narrows the differential diagnosis toward sexually transmitted infections and reactive processes.
2
Evaluate the specific musculoskeletal and dermatologic findings.
The patient has marked tenderness along tendon sheaths (Achilles, wrist dorsum) without significant joint effusion, indicating tenosynovitis rather than true arthritis. She also has discrete necrotic pustules on distal extremities.
Specific physical examination findings are critical for differentiating causes of polyarthralgia; tenosynovitis and pustular dermatitis are highly specific morphologic clues.
3
Synthesize the findings to formulate the most likely diagnosis.
The combination of migratory polyarthralgia, tenosynovitis, and a characteristic vesiculopustular rash in a sexually active patient points directly to disseminated gonococcal infection.
Recognizing this classic triad allows for prompt identification of the disease, even when localized genitourinary symptoms (e.g., cervicitis) are absent.

Key Concept

Disseminated gonococcal infection classically presents with a triad of polyarthralgia, tenosynovitis, and dermatitis (necrotic pustules), often without symptomatic primary mucosal infection in women.
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Formulating a Differential Diagnosis

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