Patients present with fever, a characteristic red rash from trunk or face to the extremities, watery diarrhea, nausea, vomiting, and hepatitis within seven to ten days following the transfusion. The rash may progress to blister-like lesions and erythroderma. Pancytopenia will develop due to the immune destruction of the recipient's bone marrow. The low platelet count causes hemorrhaging while a low white blood cell count can lead to infection. Most patients die within one to three weeks after the onset of symptoms.
The diagnosis is often missed and is usually made too late or after death. Routine laboratory studies are not helpful. The only definitive method is the identification of donor lymphocytes in the circulation or tissues of the recipient, which is accomplished through human leukocyte antigen (HLA) typing or cytogenic analysis.