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Internal Medicine

Training Level

Resident PGY 2


Henry Ford Hospital


Procalcitonin has been studied as a marker of bacterial lung infection. It frequently guides clinical practice and antibiotic management. However, procalcitonin is known to have false positive results in certain scenarios. This case describes an 86 year old African American woman with mantle cell lymphoma who presented with acute on chronic dyspnea. Diagnostic tests found a white blood cell count of 632 k/uL (95% lymphocytes) and procalcitonin of 1.29 ng/mL. Computed tomography of the chest demonstrated a right lung consolidation and hilar lymphadenopathy. She was treated empirically for pneumonia with ceftriaxone and azithromycin. Additionally, she received induction chemotherapy with rituximab and bendamustine. By hospital day three, she demonstrated clinical improvement despite a significant rise in her procalcitonin level to 42.83 ng/ml. This increase correlated with receiving rituximab. She continued to improve and was discharged to a rehab facility after finishing her induction chemotherapy. This case demonstrates a link between rituximab and false positive results of procalcitonin. Thus, clinicians should be aware of the limitations of procalcitonin as the exclusive marker in pneumonia diagnosis.

Presentation Date


Rituximab-induced Procalcitonin Elevation