Malignant syphilis (MS) is a rare form of secondary syphilis with grotesque skin lesions, systemic manifestation and life-threatening complications. This article presents a case of MS in an immunocompetent 41-year-old female, who initially manifested with a generalized nonpruritic erythematous rash and systemic symptoms. She was mistreated for generalized impetigo and hepatitis attributed to chronic alcoholism. After partial recovery and a 3-month latent period, she developed infiltrated plaques with crusts on the trunk, head and neck; pharyngitis and laryngeal lesions; generalized lymphadenopathy and nonspecific systemic symptoms. Serologic tests confirmed syphilis, and cerebrospinal fluid analyses indicated the presence of anti-treponemal antibodies. Urine drug screening was positive for cannabinoids. The polymerase chain reaction from skin biopsy samples identified T. pallidum, confirmed with Warthin-Starry staining. Immunohistochemical analysis was uncharacteristic. Tertiary syphilis, neurosyphilis, ocular syphilis and otosyphilis were excluded. However, the patient was treated for neurosyphilis with benzylpenicillin (18 million IU intravenously daily, 14 days) and corticosteroids. No Jarisch-Herxheimer reaction occurred. Ten months after treatment, residual scars were visible, and 1 year later, she attempted suicide. Since MS can resemble other diseases, it should be suspected in a mentally ill patient with chronic drug abuse,systemic nonspecific manifestations and dermatological abnormalities, including the head and neck region.