Acute transverse myelitis is a pathological condition leading to the damage of the spinal cord’s structures. It is also a rare manifestation of systemic lupus erythematosus affecting 1 to 2% of patients. It usually occurs shortly after the diagnosis is established, most often within the first five years of the disease. This article reports a 35-year-old man, with no history of any diseases, who suddenly had the following signs and symptoms: deterioration of mood, hyperhidrosis, headaches, thoracic-lumbar spine pain, sensory disorders around the torso, difficulties urinating and defecating. Magnetic resonance imaging of the spine revealed long-segment myelitis. In order to establish the aetiology of the disease, a number of laboratory and imaging examinations were performed. Based on the Systemic Lupus International Collaborating Clinics/American College of Rheumatology criteria – SLICC–ACR 2012, systemic lupus erythematosus was diagnosed. The patient was subjected to glucocorticosteroid pulse therapy without delay, and eventually improved satisfactorily. The reported case shows that transverse myelitis may be the first clinical manifestation of systemic lupus erythematosus. The authors have highlighted the necessity of an early diagnosis as well as establishing the disease’s aetiology and determining the risk of relapse, as all three affect prognosis.