Infectious Disease · Sexually Transmitted Infections
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Chancroid is caused by the gram-negative rod Haemophilus ducreyi.
The classic presentation is a painful genital ulcer with a necrotic, friable base and ragged, undermined borders.
Patients frequently present with painful, suppurative inguinal lymphadenopathy, often referred to as a bubo.
The diagnosis is primarily clinical (CDC "probable diagnosis" criteria), but can be supported via a CLIA-validated PCR test (no FDA-cleared assay exists) or culture on specialized enriched media (e.g., chocolate/GC agar with hemoglobin and IsoVitaleX), which has <80% sensitivity.
The first-line treatment for chancroid is a single dose of intramuscular ceftriaxone or a single dose of oral azithromycin.
Chancroid is a painful ulcer, which helps clinically distinguish it from the painless ulcer of primary syphilis.
The ulcer of chancroid is typically deep and purulent, contrasting with the shallow and clean-based ulcer of herpes simplex virus.
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A 24-year-old male presents to the clinic complaining of a painful sore on his penis that appeared 4 days ago. Physical examination reveals a 1.5 cm ulcer with a necrotic, friable base and ragged, undermined borders. He also has a tender, fluctuant inguinal lymph node on the right side. He reports unprotected sexual intercourse with a new partner two weeks ago. He has no history of similar lesions.
What is the most likely diagnosis?
Chancroid
The combination of a painful genital ulcer with ragged, undermined borders and painful, suppurative inguinal lymphadenopathy (bubo) is highly characteristic of / classic for chancroid caused by Haemophilus ducreyi, consistent with CDC's clinical "probable diagnosis" criteria (after excluding syphilis and HSV).
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Etiology / Epidemiology
Caused by Haemophilus ducreyi. Unprotected sexual contact is the primary risk factor.
Clinical Manifestations
Presents as a painful genital ulcer with a bubo (suppurative inguinal lymphadenopathy).
Diagnosis
Diagnosis is primarily clinical (CDC "probable diagnosis" criteria); culture on special media is the CDC criterion for definitive diagnosis (<80% sensitivity), though no FDA-cleared PCR assay exists.
Treatment
Azithromycin 1g PO once is the first-line therapy.
Prognosis
Ulcers typically heal in 1-2 weeks with appropriate antibiotic therapy.
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Epidemiology & Etiology
Caused by the fastidious gram-negative rod Haemophilus ducreyi. It is most prevalent in tropical regions and associated with unprotected sexual contact and low socioeconomic status. Outbreaks are rare in the US but should be considered in patients with travel history.
Pertinent Anatomy
Infection typically occurs on the external genitalia. The lymphatic drainage of the genitalia leads to the inguinal lymph nodes, which explains the characteristic bubo formation.
Pathophysiology
The bacteria enter through micro-abrasions during intercourse. It induces a localized inflammatory response leading to a necrotic ulcer. The infection spreads to regional lymph nodes, causing intense inflammation and potential fluctuant rupture.
Clinical Manifestations
The hallmark is a painful genital ulcer with a ragged, undermined border and a purulent base. Unlike syphilis, the ulcer is notably painful. Regional lymphadenopathy develops in ~50% of patients; of these, roughly 25% progress to a suppurative, fluctuant bubo that may rupture if left untreated.
Diagnosis
Diagnosis is primarily clinical, based on CDC "probable diagnosis" criteria (painful ulcer(s) plus consistent lymphadenopathy, with negative syphilis and HSV testing). Culture on specialized enriched media (e.g., chocolate/GC agar with hemoglobin and IsoVitaleX) is the CDC criterion for definitive diagnosis but is fastidious with <80% sensitivity; no FDA-cleared PCR assay is currently available, though CLIA-validated laboratory-developed PCR tests are more sensitive than culture where available. Rule out other STIs, specifically syphilis (via RPR/VDRL) and HSV (via PCR), as co-infection is common.
Treatment
Azithromycin 1g PO or Ceftriaxone 250mg IM are the first-line agents. Do not use fluoroquinolones in pregnant patients. Fluctuant buboes may require needle aspiration to prevent spontaneous rupture.
Prognosis
With treatment, ulcers usually show improvement within 7 days. Failure to heal suggests either misdiagnosis or HIV co-infection, which is a major risk factor for treatment failure.
Differential Diagnosis
Syphilis: painless, indurated ulcer (chancre)
Herpes Simplex: painful, grouped vesicles on an erythematous base
Lymphogranuloma Venereum: small, painless ulcer followed by painful lymphadenopathy
Granuloma Inguinale: painless, beefy-red, friable ulcer
Chancroid: painful, ragged ulcer with suppurative lymphadenopathy