Haemophagocytic lymphocytic histiocytosis (HLH) is a rare, life-threatening condition caused by abnormal activation of cytotoxic T lymphocytes, natural killer cells and macrophages resulting in hypercytokinaemia and immune-mediated injury of multiple organ systems. Secondary HLH occurs in the setting of a malignant, infectious or autoimmune stimulus. Macrophage activation syndrome (MAS) is the term used to describe HLH that develops secondary to rheumatological diseases such as lupus and juvenile idiopathic arthritis, among others. Commonly observed and documented symptoms include fever, organomegaly and lymphadenopathy. Given the potential for multiorgan failure in HLH/MAS, early identification, diagnosis and initiation of treatment is essential. We present a case of secondary HLH/MAS with acute inflammatory gastroenteritis in a middle-aged woman with a history of systemic lupus erythematosus.