A 47-year-old man presented with fever, a maculopapular rash of the palms and soles, muscular weakness, weight loss, faecal incontinence, urinary retention and mental confusion with 1 month of evolution. Neurological examination revealed paraparesis and tactile hypoesthesia with distal predominance, and no sensory level. Laboratory investigations revealed a venereal disease research laboratory (VDRL) titre of 1/4 and Treponema pallidum haemagluttin antigen (TPHA) of 1/640, positive anti-nuclear antibodies of 1/640 and nephrotic proteinuria (3.6 g/24 h). Lumbar puncture excluded neurosyphilis, due to the absence of TPHA and VDRL. The diagnosis of systemic lupus erythematosus (SLE) was established and even though transverse myelitis as a rare presentation of SLE has a poor outcome, the patient improved with cyclophosphamide, high-dose corticosteroids and hydroxychloroquine. A diagnosis of secondary syphilis was also established and the patient was treated with intramuscular benzathine penicillin G.