Graft-versus-host disease (GVHD) is a complication that can happen after a bone marrow or stem cell transplant, where immune cells from the donor recognize the recipient’s body as foreign and attack it. It primarily affects the skin, liver, and digestive tract, though the chronic form can involve nearly every organ system. Roughly 16% of allogeneic transplant recipients now develop moderate-to-severe GVHD, a rate that has dropped significantly from nearly 50% in earlier decades thanks to better prevention strategies.
How GVHD Develops
Before a transplant, the recipient undergoes intense chemotherapy or radiation to destroy their diseased bone marrow. This preparation phase does more than clear space for new cells. It damages tissues throughout the body, triggering a wave of inflammatory signals and making the recipient’s cells more visible to the incoming donor immune system.
Once the transplanted cells are infused, donor T cells (a type of white blood cell that normally fights infections) encounter the recipient’s cells and recognize them as foreign based on differences in surface proteins. Even with careful donor matching, small protein differences are enough to set off an immune response. The donor T cells multiply rapidly and release inflammatory signals that recruit additional immune cells, including natural killer cells and macrophages. These activated cells then migrate to target organs, particularly the skin, liver, and gut, where they cause direct tissue damage.
This cascade unfolds in three overlapping phases: tissue damage from pre-transplant conditioning, activation and multiplication of donor T cells, and the attack on recipient organs. The severity depends on how different the donor and recipient are at the molecular level, and on how aggressively the donor immune cells respond.
Acute vs. Chronic GVHD
GVHD comes in two distinct forms, and the distinction is based on symptoms rather than timing. Before 2005, doctors drew a hard line at day 100 after transplant: anything before was “acute,” anything after was “chronic.” That system has been replaced. Acute and chronic GVHD are now recognized as separate clinical syndromes that can overlap in time.
Acute GVHD typically appears within the first 100 days but can also show up later, in which case it’s called late acute GVHD. It targets three main organ systems: the skin (rash), the liver (elevated bilirubin causing jaundice), and the gastrointestinal tract (nausea, vomiting, diarrhea). Doctors grade its severity from I to IV based on how much skin is involved, how impaired liver function is, and the volume of diarrhea. Grade I involves a limited skin rash with no other organ involvement. Grade IV means severe damage to the skin, liver, or gut, potentially including blistering, peeling skin, or bloody stool.
Chronic GVHD is a different disease. Most cases are diagnosed within the first year after transplant, though 5% to 10% of affected patients develop symptoms later. About 30% of chronic GVHD cases appear without any preceding acute episode. Early signs often include an inflammatory skin rash, dry or irritated eyes, and oral dryness or sensitivity. More difficult manifestations can develop over time, including hardening or tightening of the skin, a lung condition called bronchiolitis obliterans that causes progressive shortness of breath, persistent oral ulcers, and inflammation of the membranes lining the chest or abdomen. Chronic GVHD can affect nearly any organ system and often resembles autoimmune diseases in its behavior.
Who Is Most at Risk
The single biggest factor influencing GVHD risk is how closely the donor and recipient match at a molecular level. Transplant teams compare proteins at six key genetic locations. Mismatches at any of these increase the risk of severe GVHD, though not all mismatches carry equal weight. A large analysis of over 10,000 transplants confirmed that closer matching significantly lowers both GVHD rates and improves survival.
Beyond matching, several other factors raise risk. Older donor age is associated with worse outcomes. Female donors who have been pregnant at least once carry a higher risk of causing chronic GVHD, likely because pregnancy exposes the immune system to foreign proteins and primes it to react. The source of stem cells also matters. Peripheral blood stem cells (collected from circulating blood) tend to carry more T cells than bone marrow, which can increase GVHD risk. Cord blood transplants have their own profile of risk that depends on both matching and cell dose.
For patients receiving transplants from half-matched (haploidentical) family donors, a specific medication given shortly after transplant has proven effective at overcoming the higher mismatch risk, making these transplants increasingly viable.
How GVHD Is Prevented
Every allogeneic transplant recipient receives preventive medications to suppress the donor immune cells before they can mount a full attack. The most common regimen combines a calcineurin inhibitor, which blocks T cell activation, with short courses of a cell-growth inhibitor given in the days immediately following transplant. According to a European transplant survey, about 61% of centers use this combination for patients receiving full-intensity conditioning.
For patients receiving reduced-intensity conditioning (a gentler pre-transplant regimen), the standard prevention typically pairs the calcineurin inhibitor with a different immune-suppressing drug that works by slowing the production of new immune cells. These preventive regimens don’t eliminate GVHD entirely, but they substantially reduce its incidence and severity.
Treatment When GVHD Develops
Corticosteroids are the cornerstone of initial treatment. The standard approach uses a high-dose steroid regimen, though research has shown that patients with mild to moderate symptoms (rash covering less than half the body and manageable diarrhea) can often be treated with lower doses without compromising outcomes. Some patients do well with a combination of lower-dose systemic steroids and a targeted steroid that acts locally in the gut with limited absorption into the bloodstream.
The challenge comes when GVHD doesn’t respond to steroids, which is called steroid-refractory disease. For steroid-refractory acute GVHD, a medication that works by blocking specific signaling pathways in immune cells received FDA approval in 2019 and remains the only approved option. It can be used in adults and children 12 and older.
Chronic GVHD that doesn’t respond to initial treatment has three FDA-approved options. The first, originally developed for blood cancers, works by inhibiting an enzyme involved in B cell signaling. The second targets a different immune signaling pathway and is approved for patients who have tried at least two prior treatments. The third is the same immune-pathway blocker used for acute GVHD, approved at a higher dose for chronic disease after one or two failed treatment lines. All three are oral medications taken daily.
Living With GI Symptoms
Gastrointestinal GVHD is one of the most disruptive manifestations, causing nausea, cramping, and diarrhea that can range from mild to severe. Nutritional support plays a meaningful role in recovery. Research suggests that patients who maintain oral intake, even in small amounts, tend to do better than those who rely entirely on intravenous nutrition. When the gut is severely inflamed, doctors often start with IV nutrition but reintroduce food gradually as soon as it can be tolerated.
Many transplant centers now recommend a lactose-free diet for patients with intestinal GVHD. Animal studies have shown that removing lactose reduces the growth of certain bacteria associated with worsening GVHD, and clinical practice has followed suit. A stepwise approach to reintroducing foods, starting with the most easily tolerated items and gradually expanding, has shown benefits in pediatric patients and is widely applied to adults as well. Interestingly, one study found that patients receiving home care had less GVHD than those staying in the hospital, partly attributed to better oral intake in a home setting, where food is more familiar and appetizing.
The Graft-Versus-Leukemia Effect
One of the complications of managing GVHD is that the same donor immune response that damages healthy tissue also attacks residual cancer cells. This is called the graft-versus-leukemia (or graft-versus-tumor) effect, and it’s one of the main reasons allogeneic transplants work as a cancer treatment. Completely eliminating the donor immune response would reduce GVHD but could also increase the risk of cancer relapse. Certain types of donor-recipient mismatches actually lower relapse risk even as they increase GVHD risk. Treatment decisions involve a constant balancing act: suppressing the immune response enough to protect healthy organs while preserving enough activity to keep the cancer in check.