Merck Manual

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Sheldon R. Morris

, MD, MPH, University of California San Diego

Reviewed/Revised Jan 2023
Topic Resources

Chancroid is infection of the genital skin or mucous membranes caused by Haemophilus ducreyi and characterized by papules, painful ulcers, and enlargement of the inguinal lymph nodes leading to suppuration. Diagnosis is usually clinical because culturing the organism is difficult. Treatment is with a macrolide (azithromycin or erythromycin), ceftriaxone, or ciprofloxacin.

Haemophilus ducreyi is a short, slender, gram-negative bacillus with rounded ends.

Chancroid is a rare sexually transmitted infection (STI) in the US and other resource-rich countries, occurring primarily in occasional, local epidemics. Chancroid is a common cause of genital ulcers in resource-poor areas of Asia, Africa, and the Caribbean. Like other STIs causing genital ulcers, chancroid increases risk of HIV transmission.

General references

  • 1. Mitjà O, Lukehart SA, Pokowas G, et al: Haemophilus ducreyi as a cause of skin ulcers in children from a yaws-endemic area of Papua New Guinea: A prospective cohort study. Lancet Glob Health 2:e235–41, 2014. doi: 10.1016/S2214-109X(14)70019-1

  • 2. van Hattem JM, Langeveld TJC, Bruisten SM, et al: Haemophilus ducreyi cutaneous ulcer contracted at Seram Island, Indonesia, presented in the Netherlands. PLoS Negl Trop Dis 12(4):e0006273, 2018. doi: 10.1371/journal.pntd.0006273

Symptoms and Signs of Chancroid

After an incubation period of 3 to 7 days, small, painful papules appear on the genitals and rapidly break down into shallow, soft, painful ulcers with ragged, undermined edges (ie, with overhanging tissue) and a red border. Ulcers vary in size and often coalesce. Deeper erosion occasionally leads to marked tissue destruction.

The inguinal lymph nodes form a bubo (enlarged and tender group of regional lymph nodes). They sometimes become matted together, fluctuant, or suppurative, in some cases forming an abscess. The skin over the abscess may become red and shiny and may break down to form a sinus. The infection may spread to other areas of skin, resulting in new lesions. Phimosis Phimosis and Paraphimosis Phimosis is inability to retract the foreskin. Paraphimosis is entrapment of the foreskin in the retracted position; it is a medical emergency. Phimosis is normal in children and typically resolves... read more Phimosis and Paraphimosis , urethral stricture, and urethral fistula may result from chancroid.

Diagnosis of Chancroid

  • History and physical examination

  • Sometimes culture or polymerase chain reaction (PCR)

Chancroid is suspected in patients who have unexplained genital ulcers or buboes (swollen, tender lymph nodes that may become suppurative or form abscesses) and who are or have been in endemic areas. Genital ulcers from other causes (see table ) may resemble chancroid.

Diagnosis is usually based on clinical findings alone because culture of the bacteria is difficult and microscopic identification is confounded by the mixed flora in ulcers.

If available, a sample of pus from a bubo or exudate from the edge of an ulcer should be sent to a laboratory that can identify H. ducreyi. PCR testing is not commercially available, but several institutions have certified tests that are highly sensitive (98.4%) and specific (99.6%) for H. ducreyi. Clinical diagnosis has a lower sensitivity (53 to 95%) and specificity (41 to 75%).

Serologic testing for syphilis and HIV and cultures for herpes should be done to exclude other causes of genital ulcers. However, interpretation of test results is complicated by the fact that genital ulcers due to other conditions may be coinfected with H. ducreyi.

Treatment of Chancroid

  • Antibiotics (various)

Treatment of chancroid should be started promptly, without waiting for test results. One of the following is recommended:

  • A single-dose of azithromycin 1 g orally or ceftriaxone 250 mg IM

  • Erythromycin 500 mg orally 3 times a day for 7 days

  • Ciprofloxacin 500 mg orally twice a day for 3 days

Patients treated for other causes of genital ulcers should be given antibiotics that also treat chancroid if chancroid is suspected and laboratory testing is impractical.

Treatment of patients with HIV coinfection, particularly with single-dose regimens, may be ineffective. In these patients, ulcers may require up to 2 weeks to heal, and lymphadenopathy may resolve more slowly.

Buboes can safely be aspirated for diagnosis or incised for symptomatic relief if patients are also given effective antibiotics.

Sex partners should be examined and treated if they had sexual contact with the patient during the 10 days before the patient’s symptoms began.

Patients with chancroid should have a serologic test for syphilis and HIV 3 months after being diagnosed with chancroid.

Drugs Mentioned In This Article

Drug Name Select Trade
Azasite, Zithromax, Zithromax Powder, Zithromax Single-Dose , Zithromax Tri-Pak, Zithromax Z-Pak, Zmax, Zmax Pediatric
A/T/S, Akne-mycin, E.E.S., Emcin Clear , EMGEL, E-Mycin, ERYC, Erycette, Eryderm , Erygel, Erymax, EryPed, Ery-Tab, Erythra Derm , Erythrocin, Erythrocin Lactobionate, Erythrocin Stearate, Ilosone, Ilotycin, My-E, PCE, PCE Dispertab , Romycin, Staticin, T-Stat
Ceftrisol Plus, Rocephin
Cetraxal , Ciloxan, Cipro, Cipro XR, OTIPRIO, Proquin XR
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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