Aphthous ulcers are typically found inside the mouth, not on the genitals, and lack the associated painful inguinal lymphadenopathy of chancroid.
While causing painful genital ulcers, Behcet's is a systemic disease distinguished by the presence of recurrent oral ulcers and other systemic signs like uveitis.
This is a recurrent lesion in the exact same spot triggered by a specific drug, unlike the infectious etiology of chancroid.
This is characterized by painless, progressive, "beefy-red" ulcerative lesions that are highly vascular and bleed easily, unlike the painful, purulent ulcer of chancroid.
Genital herpes is distinguished by its initial presentation as a group of vesicles that then evolve into ulcers, whereas chancroid begins as a papule or pustule.
Pemphigus vegetans can cause genital lesions, but these are typically fungating, vegetative plaques, not a discrete, painful ulcer.
A cancerous ulcer would be chronic, non-healing, and have firm, indurated borders, unlike the acute, soft ulcer of chancroid.
The primary chancre of syphilis is classically a single, painless ulcer with a clean base and firm, indurated border, which is the opposite of the painful, purulent, soft ulcer of chancroid.
