- absolute neutrophil count (ANC) <500 cells/microL, platelet count <40,000 cells/microL, serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), or total bilirubin >5x the age specific upper limit of normal, acute or chronic renal insufficiency with a baseline creatinine clearance of <60 mL/minute or requires dialysis therapy for any reason, or are profoundly immunodeficient and require prophylactic antimicrobial therapy for Pneumocystis jirovicei, Toxoplasma gondii, or herpes viruses, and/or chronic or intermittent immunoglobin replacement therapy.