Chancroid is a sexually transmitted genital ulcer disease (GUD) caused by the gram-negative bacillus Haemophilus ducreyi. Chancroid is characterized by the presence of painful ulcers (see image below) and inflammatory inguinal adenopathy.
Multiple nonindurated ulcers with ragged edges may develop around the initial ulcer. Painful inguinal lymphadenitis (bubo) can develop, and the lymph node may suppurate and drain to the skin, resulting in ulceration.
Chancroid usually starts as a small papule that rapidly becomes pustular and eventually ulcerates. The ulcer enlarges, develops ragged undermined borders, and is surrounded by a rim of erythema. Unlike syphilis, lesions are tender and the border of the ulcer is not indurated. Courtesy of Hon Pak, MD.
Chancroid is often referred to as a soft chancre because the lesions are usually not indurated. In contrast, a syphilitic chancre is nontender and indurated. The identification of the causative agent of chancroid was first reported in 1889 by August Ducrey, following experiments in which he autoinoculated patients’ forearms with pus from their genital ulcers.