hospital, and typically involves the skin, GI tract, or liver Chronic GVHD presents after 100 days and is accompanied by severe immunologic dysfunction The evaluation of patients with known or suspected GVHD following an allogeneic stem cell transplant should include assessment of potential dehydration or anemia due to colitis or dyspnea due to lung involvement Physical examination should assess the skin for rash, fibrosis, or jaundice, liver size and tenderness, and oxygen saturation, with a focus on screening for organ dysfunction serious enough to require intervention in the ED Clinicians should have a low threshold for admitting such patients for inpatient management due to overall fragility of this patient population Therapy for GVHD is primarily immunosuppressive using corticosteroids, cyclosporine, and other agents directed against T cells Specialists in hematopoietic stem cell transplant decide whether to pursue such agents and when Often a biopsy (skin, bowel, liver, etc.) is required to diagnose GVHD on histopathology The management of infectious complications for patients following stem cell transplant is not inherently different from the oncology population overall, but the relevant organisms may vary and the clinician’s level of suspicion may need to be higher ( Table 98.11 ) Infections in these patients result from the extreme immunosuppression achieved by myeloablation, cutaneous and mucosal barrier damage intrinsic to the transplant process, and the immunologic immaturity of the transplanted marrow Central lines exacerbate this risk Importantly, the types of infections patients tend to develop after hematopoietic stem cell transplant can vary based on how many days have elapsed since the transplant In the first month after the transplant, as patients are hospitalized and awaiting engraftment of their bone marrow, they are vulnerable to gram-positive and gramnegative bacteria, anaerobic bacteria, respiratory viruses, reactivation of herpes simplex virus, and fungal infection with candida and aspergillus After engraftment, from day 30 to 100 after the transplant, patients remain at risk for bacterial infections, particularly those related to their central lines Aspergillus and respiratory viruses continue to be a concern However, CMV, pneumocystis, and toxoplasma become more of a threat at this point More than 100 days after the transplant, patients are at risk for encapsulated bacteria, especially if they are simultaneously affected by GVHD or ongoing immunosuppression Aspergillus, pneumocystis, and toxoplasma continue to be a concern Viral infections with varicella zoster virus, CMV, EBV, and respiratory viruses are also a large threat for these patients When patients present to the ED with fever following a hematopoietic stem cell transplant, empiric coverage with antibiotics should be instituted quickly while