Perforin deficiency is known to induce complex changes in leukocyte populations in humans and mice [16, 17, 20], including a classical presentation of familial hemophagocytic lymphohistiocytosis, characterized by early life onset, high mortality, and multiple immunological defects, including uncontrolled activation and proliferation of CD4+ and CD8+ T cells, cytokine storm, macrophage activation and proliferation, pancytopenia, and anemia [20]. This evidence concerns the gene PRF1 and hyperinsulinemic hypoglycemia, familial, 4.