Clinical meaning
Graft-versus-host disease (GVHD) occurs when immunocompetent donor T-lymphocytes in transplanted tissue recognize the recipient's cells as foreign and mount an immune attack against the host's organs. GVHD most commonly occurs after allogeneic hematopoietic stem cell transplant (HSCT) but can also occur after blood transfusion in immunocompromised patients (transfusion-associated GVHD, which is nearly 100% fatal). Three conditions are required (Billingham criteria): the graft must contain immunocompetent cells, the host must express tissue antigens absent from the donor, and the host must be unable to mount an effective response to reject the donor cells. Acute GVHD (within 100 days) primarily affects skin (maculopapular rash), liver (jaundice, elevated bilirubin), and GI tract (severe diarrhea, abdominal pain). Chronic GVHD (after 100 days) resembles autoimmune diseases with scleroderma-like skin changes, sicca syndrome, and bronchiolitis obliterans.
Exam relevance
Risk factors: - HLA mismatch between donor and recipient in stem cell transplant - Unrelated donor transplant (higher risk than matched sibling) - Older recipient age at time of transplant - Prior acute GVHD predisposing to chronic GVHD - Transfusion of non-irradiated blood products to immunocompromised patients