Chancroid

Chancroid (also known as soft chancre) is a highly contagious sexually transmitted infection (STI) caused by Haemophilus ducreyi. Although chancroid is a rare infection in the US, it may occur in immunocompromised patients and is a common cause of genital ulcers in tropical and subtropical regions. It is characterized by the formation of small, painful ulcers on the genitalia and regional lymphadenopathy. The diagnosis is primarily based on clinical findings and is probable if genital herpes and syphilitic chancre have been ruled out. Culture confirms the diagnosis but is not widely available. Treatment usually involves administration of an antibiotic such as ceftriaxone or azithromycin.

• Pathogen: Haemophilus ducreyi
• Transmission: sexually transmitted infection

References:^[1]

• Incubation period: typically 4–10 days
• Clinical features
  • Very painful genital ulcers
    • Deep, small (∼ 10–20 mm in diameter), well-demarcated lesions with a grayish necrotic base
  • Painful inguinal lymphadenopathy
  • An asymptomatic course is more likely in women.

In contrast to chancre, chancroid is often painful: The causative pathogen is Haemophilus du-creyi ("do cry")!

References:^[1][2][3]

Chancroid is a clinical diagnosis. Microbiological analysis or culture may confirm the diagnosis, but have limited sensitivity and are often time consuming.

• Microbiological analysis
  • Gram-stain: gram-negative rods in ulcer exudate (swab sample) suggestive of Haemophilus ducreyi infection
  • Dark field examination for Treponema pallidum and HSV PCR to rule out primary syphilis and genital herpes, respectively
• Culture: confirms diagnosis (not always conducted)

References:^[1][4]

• See differential diagnosis of other genital lesions.

The differential diagnoses listed here are not exhaustive.

• Antibiotic treatment: : single dose oral azithromycin or IM ceftriaxone
• Examine and treat sexual partner(s).

References:^[4]