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Difficulty: MediumFormulating a Differential Diagnosis

During a visit to a sexual health clinic, a 2929-year-old male is evaluated for a rapidly enlarging, painful lump in the right groin area that has made walking difficult over the past week. He mentions that approximately three weeks prior, he had a small, painless sore on the coronal sulcus of his penis that completely resolved without any medical intervention. He is sexually active with several male partners and occasionally uses recreational drugs. Vital signs reveal a temperature of 37.9∘C37.9^\circ\text{C} (100.2∘F100.2^\circ\text{F}), pulse of 88/min88/\text{min}, and blood pressure of 118/76 mm Hg118/76\text{ mm Hg}. Genitourinary examination demonstrates no active ulcerative lesions. However, there is marked right inguinal lymphadenopathy that is tender and fluctuant, with a palpable horizontal indentation dividing the swelling into upper and lower masses. A rapid plasma reagin (RPR) test is nonreactive. Which of the following is the most likely diagnosis?

  1. Lymphogranuloma venereumAnswer
  2. B
    Primary syphilis
  3. C
    Chancroid
  4. D
    Granuloma inguinale
  5. E
    Genital herpes

Answer

Lymphogranuloma venereum
The correct diagnosis is Lymphogranuloma venereum (LGV), caused by Chlamydia trachomatis serovars L1-L3. The classic presentation involves a primary stage characterized by a small, painless genital ulcer that heals spontaneously within a few days. This is followed 2 to 6 weeks later by the secondary stage, which features painful, severe, and fluctuant regional lymphadenopathy (buboes). The palpable horizontal indentation described in the physical examination is the 'groove sign,' caused by the enlargement of both inguinal and femoral lymph nodes separated by the inguinal ligament (Poupart's ligament). This clinical timeline and physical finding are highly specific for LGV.

Step-by-Step Solution

1
Analyze the initial presentation from the patient's history.
The patient experienced a single, small, painless genital ulcer that resolved spontaneously 3 weeks ago.
Establishing the nature of the initial ulcer helps rule out conditions characterized by painful ulcers, such as chancroid and genital herpes.
2
Evaluate the current physical examination findings.
The patient now has painful, fluctuant right inguinal lymphadenopathy with a palpable horizontal groove.
This identifies the secondary stage of the disease. The indentation (groove sign) is formed by the inguinal ligament separating enlarged inguinal and femoral lymph nodes.
3
Synthesize the timeline and physical findings to formulate the most likely differential diagnosis.
The biphasic clinical course (painless ulcer followed weeks later by painful suppurative buboes with a groove sign) strongly points to Lymphogranuloma venereum.
Other genital ulcer diseases do not perfectly align with this specific chronological progression and unique lymph node morphology.

Key Concept

Differentiating genital ulcer diseases based on ulcer pain, lymphadenopathy characteristics, and chronological progression.
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Topics

Formulating a Differential Diagnosis

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