Pneumocystis jiroveci pneumonia is a life-threatening infection that occurs after allo-SCT. Without prophylaxis, 5–16% of patients develop pneumocystis pneumonia with a median onset at 9 weeks after transplantation and a mortality rate of 76%. Risk factors for pneumocystis pneumonia after allo-SCT include immunosuppressive therapy, chronic GVHD, relapse of primary disease or low CD4⁺ T cell count (<200 cells per μL). As the introduction of trimethoprim–sulfamethoxazole as prophylaxis against pneumocystis, the incidence of pneumocystis pneumonia after allo-SCT has decreased to less than 5%, and most cases of the disease develop after discontinuation of the drug at more than 6 months after transplantation. Alternative drugs include aerosolized pentamidine, dapsone and atovaquone;⁶ however, they are less effective than trimethoprim–sulfamethoxazole. Moreover, compared with prophylaxis with trimethoprim–sulfamethoxazole, that with aerosolized pentamidine is associated with increased mortality at 1 year after allo-SCT.

Source:Nature.