CD27 and hyperinsulinemic hypoglycemia, familial, 4: Finally, immune activation fulfilling the clinical criteria of HLH occasionally occurs in several additional primary immunodeficiencies, including SCID, some combined immunodeficiencies such as Wiskott-Aldrich syndrome, CD27 deficiency and ITK deficiency, chronic granulomatous disease (CGD) and IFNγ receptor deficiency (35, 36) (Figures 1B,C).