A Rare Case of Eltrombopag-Induced Pneumonitis

Abstract

Introduction Immune thrombocytopenia (ITP) is an acquired thrombocytopenia due to autoantibodies. Eltrombopag is a thrombopoietin receptor agonist (TPO-RA) used as a second-line agent in the setting of persistent or chronic ITP. Potential severe adverse effects include hepatotoxicity, thromboembolism, and increased risk of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). Upper respiratory infections and pharyngitis have also been described, but to our knowledge, no known cases of eltrombopag-induced pneumonitis have been reported to date. Case Presentation We present a 68-year-old male with a history of recent onset ITP, stage IV mantle cell lymphoma (in remission), and Pneumocystis pneumonia who was initiated on eltrombopag 11 days prior to admission for ITP refractory to corticosteroid therapy. Three weeks prior to admission, the patient underwent a bone marrow biopsy without evidence of monoclonal B cells or immunophenotypically abnormal T cell populations. Following initiation of eltrombopag, the patient had progressive dyspnea on exertion associated with subjective fevers and chills requiring hospitalization. Oxygen saturation was 88% on room air with exam notable for coarse crackles to the bilateral lung bases. CT angiogram of the chest revealed bilateral pulmonary emphysema, ground glass opacities, and bilateral bronchiectasis most pronounced in the lower lobes (Figure 1). No pulmonary embolism or mediastinal adenopathy was identified. Cytomegalovirus DNA, aspergillus antigen, and COVID-19 NAAT testing were negative. A respiratory viral panel was positive for Rhinovirus. Bronchoalveolar lavage (BAL) and right middle lobe lung parenchymal biopsy were subsequently performed. Pathology demonstrated focal intra-alveolar organization and fibroblast plugs, interstitial fibrosis, pneumocyte hyperplasia, and mixed (predominantly chronic) inflammatory infiltrate (Figure 2a & 2b). BAL was negative for malignant cells. Pneumocystis jirovecii DNA was detected, but < 250 copies/mL were identified and thus was thought to be less likely contributing to the disease process.Given the suspicion for eltrombopag-induced pneumonitis, the patient was initiated on high-dose corticosteroid therapy with a slow taper over the span of several weeks. Following initiation of corticosteroids, the patient was noted to have gradual improvement in his respiratory status. The patient was ultimately discharged on room air 1 month later due to other hematologic complications necessitating a prolonged hospital stay. Discussion The exact mechanism of eltrombopag-induced pneumonitis is unclear, although we postulate that it is related to an exaggerated immune response involving T-cell homeostasis resulting in alveolarcapillary permeability, inflammation, and fibrosis. Suspicion for eltrombopag-induced pneumonitis should prompt initiation of early corticosteroid therapy to prevent acute and chronic complications of pneumonitis. (Figure Presented).