CAT and macrophage activation syndrome: Patients may be infected with various catalase-positive pathogens (e.g., Staphylococcus aureus, Aspergillus, Serratia, Burkholderia, Nocardia) and, in severe cases, may develop macrophage activation syndrome or hemophagocytic lymphohistiocytosis (4, 10–12), complicating the diagnosis.