Graft vs. Host Disease (GVHD) occurs when transplanted stem cells from a donor attack the recipient's body, potentially affecting several organs. GVHD may manifest as either acute or chronic, with acute GVHD typically developing within 100 days of transplantation and affecting the skin, gastrointestinal tract, and liver, while chronic GVHD can impact multiple organs over a longer period. Causes of GVHD include immune responses triggered by mismatched human leukocyte antigens (HLAs) between donor and recipient. Diagnosis relies on symptom observation and ruling out other conditions, as no specific test exists. Treatments often involve immunosuppressants like corticosteroids and biologics, though severe cases may require hospitalization, and prevention focuses on HLA matching and prophylactic medications.

GVHD is categorized into acute and chronic types based on the timing of symptom onset, with acute GVHD developing within 100 days post-transplant and affecting up to 70% of recipients, and chronic GVHD occurring after 100 days and affecting 40-50%.

Symptoms of acute GVHD include a rash, severe diarrhea, and liver dysfunction detectable only through tests unless severe, while chronic GVHD may cause dry mouth, skin thickening, and organ-specific symptoms.

The primary cause of GVHD is the immune response triggered when donor-derived new immune cells recognize the recipient's cells as foreign due to differences in HLAs, despite compatibility testing before transplantation.

Risk factors for developing GVHD include HLA mismatches between donor and recipient, older age, and certain gender combinations, such as male recipients receiving transplants from previously pregnant female donors.

Diagnosis of GVHD involves assessing symptoms and excluding other possible causes, while treatment typically includes immunosuppressants like corticosteroids, calcineurin inhibitors, and biologics, with severe cases potentially requiring additional therapies such as photopheresis.

Prevention of GVHD emphasizes close matching of donor and recipient HLA markers and the use of immunosuppressive drugs before and after transplantation, with FDA-approved medications like Orencia aiding in reducing the risk.

Complications of GVHD can be severe, including increased susceptibility to infections, lung disorders, and gastrointestinal issues, underscoring the importance of early diagnosis and management to improve survival rates, which vary significantly based on disease severity.