# Diagnostic Challenges of Pneumocystis jirovecii Pneumonia in Methotrexate-Induced Pancytopenia: A Report on a Fatal Case and Review of the Literature

## TL;DR

This paper reports a fatal case of Pneumocystis jirovecii pneumonia in a patient with methotrexate-induced pancytopenia and highlights the challenges in diagnosing it due to limited diagnostic options.

## Contribution

The paper introduces the use of plasma β-D-glucan and minimally invasive techniques for early detection of PCP in pancytopenic patients.

## Key findings

- Fever during methotrexate-induced pancytopenia may indicate PCP even without respiratory symptoms.
- Plasma β-D-glucan and high-resolution computed tomography can aid in early detection of PCP.
- Grocott-stained sputum or sputum PCR can be used when bronchoscopy is not feasible.

## Abstract

Early detection and diagnosis of Pneumocystis jirovecii pneumonia (PCP) among non-HIV patients is crucial because of its rapid course. However, when PCP is suspected due to respiratory symptoms in pancytopenia patients, performing bronchoalveolar lavage is often challenging because of progressing respiratory failure and elevated risk of bleeding.

We report the case of a 78-year-old woman with rheumatoid arthritis who developed PCP during methotrexate (MTX)-induced pancytopenia. One week before hospital admission, she presented with fever and malaise without respiratory symptoms. We made a definitive diagnosis via Grocott-stained sputum with reference to her elevated plasma β-D-glucan. Respiratory failure was already advanced at diagnosis, and the patient died on hospital day 11.

Because MTX use and MTX-induced pancytopenia increase the risk of PCP, fever during pancytopenia may indicate the need for plasma β-D-glucan and high-resolution computed tomography for its early detection and treatment, even without respiratory symptoms. Minimally invasive techniques such as Grocott-stained sputum or real-time polymerase chain reaction (PCR) of sputum may be helpful in diagnosis when bronchoscopy is not feasible due to pancytopenia.