• Stenotrophomonas maltophilia;
  • pneumonia;
  • incidence;
  • neutropenia;
  • hematologic malignancy;
  • hematopoietic stem cell transplantation



Pneumonia caused by Stenotrophomonas maltophilia is rare, but can be lethal in severely immunocompromised patients. However, its clinical course remains unclear.

Patients and methods

Patients with pneumonia caused by S. maltophilia in Toranomon Hospital (890 beds, Tokyo, Japan) were reviewed retrospectively between April 2006 and March 2010.


During the study period, 10 cases of S. maltophilia pneumonia were identified. Seven patients had acute myeloid leukemia, 2 had myelodysplastic syndrome, and 1 had malignant lymphoma. All patients developed symptoms after allogeneic hematopoietic stem cell transplantation (HSCT). Five patients received first cord blood transplantation (CBT), 4 patients received second CBT, and 1 patient received first peripheral blood stem cell transplantation (PBSCT). The overall incidence of S. maltophilia pneumonia among 508 patients who received HSCT during the period was 2.0%. The incidence was 0% (0/95) in patients after bone marrow transplantation, 0.8% (1/133) after PBSCT, and 3.2% (9/279) after CBT. Pneumonia developed a median of 13.5 days (range, 6–40) after transplantation. At onset, the median white blood cell count was 10/μL (range, 10–1900), and the median neutrophil count was 0/μL (range, 0–1720). In all patients, S. maltophilia bacteremia developed with bloody sputum or hemoptysis. The 28-day mortality rate was 100%; the median survival after onset of pneumonia was 2 days (range, 1–10).


Hemorrhagic S. maltophilia pneumonia rapidly progresses and is fatal in patients with hematologic malignancy. Attention should be particularly paid to the neutropenic phase early after HSCT or prolonged neutropenia due to engraftment failure. A prompt trimethoprim-sulfamethoxazole-based multidrug combination regimen should be considered to rescue suspected cases of S. maltophilia pneumonia in these severely immunosuppressed patients.