Hemophagocytic syndrome (HPS), which was first described in 1939, is a heterogeneous disorder characterized by excessive activation and proliferation of non-malignant macrophages. HPS can cause acute kidney injury and nephrotic syndrome; in addition, renal transplant recipients are at risk of developing HPS as a result of their immunocompromised state. This Review summarizes the presentation, causes, pathophysiology and renal features of HPS for the benefit of the practicing nephrologist.