IFNG and hemophagocytic syndrome: Hemophagocytic lymphohistiocytosis (HLH), a syndrome that bears key similarities to life-threatening COVID-19 [1–5], is characterised by phagocytosis in bone marrow and other tissues, of haemoglobin, white blood cells and platelets by histiocytes, such as macrophages, under excess stimulation by IFN-gamma.