Background Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease that has a great diversity of clinical presentations and occurs mostly in young women. However, late-onset SLE does exist and seldom presents with an atypical case, including pericardial effusion (PE). Case presentation A 64 years old Asian woman presented with weakness all over the body and slight breathlessness for the past 2 days before the hospital admission. Her initial vital signs are 80/50 mmHg for blood pressure and a respiration rate of 24 breaths/min. Rhonchi were heard on the left lung and pitting edema on both legs. No evidence of any skin rash. Laboratory examination displayed anemia, hematocrit decrement, and azotemia. A 12-lead ECG demonstrated left-axis deviation with low voltage (Fig. 1). Chest X-ray showed left massive pleural effusion (Fig. 2). Transthoracic echocardiography revealed biatrial enlargement, normal EF 60%, diastolic dysfunction grade II, and thickening of the pericardium with mild circumferential PE corresponding with effusive-constrictive pericarditis (Fig. 3). The patient also brought CT angiography and cardiac MRI result, which confirmed pericarditis with PE. Treatment was initiated in ICU with fluid resuscitation of normal saline. The patient’s routine oral treatments, including furosemide, ramipril, colchicine, and bisoprolol, were carried on. An autoimmune workup was performed by a cardiologist and demonstrated an elevation in antinuclear antibody/ANA (IF) of 1:100, which finally unveiled a diagnosis of SLE. Pericardial effusion is one critical condition to consider, despite it being an uncommon presentation in late-onset SLE. Mild pericarditis in an SLE case can be treated with corticosteroid administration. Colchicine also has been found to reduce the risk of pericarditis recurrence. However, an atypical presentation from this case led to a slightly delayed treatment that escalated the morbidity and mortality risk. The patient had a sudden cardiac arrest and passed away 3 days after being treated. Conclusions Atypical presentation during late-onset SLE, mainly in the form of pericardial effusion even constrictive pericarditis, should be taken into a consideration since they are a scarce feature in SLE patients. Swift recognition and prompt treatment are important for the optimal outcome.