Prospective study of toxoplasma reactivation by polymerase chain reaction in allogeneic stem-cell transplant recipients

Toxoplasmosis is a rare but life‐threatening complication of allogeneic stem‐cell transplantation. Polymerase chain reaction (PCR) offers the possibility to make the diagnosis earlier than conventional techniques, and is then expected to improve the prognosis. We undertook a prospective screening using a competitive PCR in blood in 32 stem‐cell transplant recipients. The sampling covered the first 150 days post‐transplant, at days 21, 30, 45, 60, 90, 120, and 150. Twenty‐four patients had anti‐toxoplasma antibodies before transplant. Three of them (12.5%) had transient PCR‐positive samples at 21, 45, and 90 days post‐transplant, respectively. The three PCR‐positive patients were febrile but had no funduscopic examination or cerebral computerised tomography (CT) scan abnormalities. The PCR signal disappeared when the patients were given trimethoprim‐sulfamethoxazole, and no full‐blown toxoplasmosis was observed. Toxoplasma reactivation evidenced using PCR is frequent in seropositive patients not receiving trimethoprim‐sulfamethoxazole during the 1–3 months post‐transplant. Toxoplasma PCR should be included in the diagnostic strategy of fever of unexplained origin in allogeneic stem‐cell transplant recipients. Then, prompt specific therapy can be initiated to avoid development of full‐blown toxoplasmosis ^Note.