Lues maligna, also known as malignant syphilis, is an uncommon variant of syphilis at the secondary
stage – more commonly reported in immunocompromised patients or those with concomitant human
immunodeficiency virus (HIV) infection. In this report, we present a case of a 28‑year‑old HIV‑negative
male with a 9‑month history of multiple, well‑defined, irregularly‑shaped, erythematous papules, and small
plaques evolving to ulcerated plaques and nodules with crusts, associated with pain, pruritus, and episodes
of fever, arthralgia, and weight loss. Positive treponemal and nontreponemal tests, aided by histopathologic
findings consistent with syphilis led to the diagnosis of lues maligna. Significant improvement of lesions
was noted with 3 weekly doses of 2.4 million units of benzathine penicillin G. For patients presenting
with painful and pruritic erythematous ulcerated plaques with crusts associated with systemic symptoms,
and with a significant sexual history despite testing negative for HIV infection, a high index of suspicion
for uncommon presentations of other sexually transmitted infections such as syphilis could aid in early
diagnosis and subsequent treatment.