Transfusion-associated graft versus host disease

Transfusion-associated graft versus host disease (TA-GvHD) is a rare complication of blood transfusion, in which the donor T lymphocytes mount an immune response against the recipient's lymphoid tissue. Donor lymphocytes are usually identified as foreign and destroyed by the recipient's immune system. However, in situations where the recipient is immunocompromised (inborn immunodeficiency, acquired immunodeficiency, malignancy), or when the donor is homozygous and the recipient is heterozygous for an HLA haplotype (as can occur in directed donations from first-degree relatives), the recipient's immune system is not able to destroy the donor lymphocytes. This can result in graft versus host disease.

Epidemiology and Pathogenesis
The incidence in immunocompromised patients receiving blood transfusions is estimated to be 0.1 - 1.0%, mortality around 80 - 90%. Mortality is higher in TA-GvHD than in GvHD associated with bone marrow transplantation, where the engrafted lymphoid cells in the bone marrow are of donor origin; therefore, the immune reaction is not directed against them.

The most common cause of death in TA-GvHD is aplastic anemia.

Clinical manifestations
The clinical presentation the same as in GvHD occurring in other settings, such as bone marrow transplantation. TA-GvHD can develop four to thirty days after the transfusion. Typical symptoms include:
 * fever
 * erythematous maculopapular rash, which can progress to generalised erythroderma
 * toxic epidermal necrolysis in extreme cases

Other symptoms can include cough, abdominal pain, vomiting, and profuse diarrhea (up to 8 liters/day).

Laboratory manifestations
Laboratory findings include pancytopenia, abnormal liver enzymes, and electrolyte imbalance (when diarrhea is present).

Diagnosis
TA-GvHD can be suspected from a biopsy of the affected skin, and established by HLA analysis of the circulating lymphocytes. This testing can identify circulating lymphocytes with a different HLA type than the tissue cells of the host.

Treatment and Prevention
Treatment is only supportive, as no available form of therapy has proven effective in treating TA-GvHD.

Prevention includes gamma irradiation of the lymphocyte-containing blood products. This procedure should be performed in transfusions when:
 * the recipient is immunocompromised
 * the blood components are from a family donor
 * HLA-matched platelets are transferred.

Another means of prevention is the use of third- or fourth-generation leukoreduction filters, although the efficacy of this procedure has not yet been documented.