Infectious Disease · Sexually Transmitted Infections
The facts most likely to be tested
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, but can be confirmed via PCR testing or culture on specialized charcoal-enriched media.
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 pathognomonic for chancroid caused by Haemophilus ducreyi.
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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
PCR is the gold standard; clinical diagnosis is often presumptive.
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. Approximately 50% of patients develop a bubo, which is a tender, fluctuant inguinal lymph node that may rupture if left untreated.
Diagnosis
Diagnosis is primarily clinical, but PCR is the gold standard for confirmation. Culture is difficult due to the fastidious nature of the organism. 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