Patients with chronic lymphocytic leukemia (CLL) treated with the Bruton’s tyrosine kinase (BTK) inhibitor, ibrutinib, may have a mildly elevated risk of developing Pneumocystis jirovecii pneumonia (PCP), according to an article published in Blood.1

Among 96 patients treated only with ibrutinib, researchers observed 5 cases of PCP; after initiating ibrutinib treatment, median time to PCP occurrence was 6 months. PCP diagnosis, however, was often delayed.

CD4 T-cell counts and immunoglobulin G levels were within normal ranges for patients with PCP, suggesting that ibrutinib was not interfering with normal immune functions.

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The authors conclude, though inconclusively, that PCP incidence may be related to BTK inhibition, suggesting a need for caution about or prophylaxis for PCP for patients receiving BTK inhibitors.

All cases of PCP, which were grade 2 or lower, were resolved with oral therapies; there were no recorded cases of recurrence.


  1. Ahn IE, Jerussi T, Farooqui M, Tian X, Wiestner A, Gea-Banacloche J. Atypical Pneumocystis jirovecii pneumonia in previously untreated patients with CLL on single-agent ibrutinib. Blood. 2016 Aug 8. doi: 10.1182/blood-2016-06-722991 [Epub ahead of print]