15. Eosinophilic pneumonitis secondary to baricitinib

INTRODUCTION: We present a case of drug-induced pneumonitis in a patient taking baricitinib. CASE DESCRIPTION: A 63-year-old patient with longstanding sero-positive erosive RA (anti-CCP >340) on long term methotrexate started taking baricitinib for his poorly-controlled arthritis 5 weeks prior to the hospital admission with two-week history of increasingly short of breath, productive cough with yellow sputum and right sided pleuritic chest pain. On examination, he was febrile with temperature 38.2, tachypnoeic, respiratory rate 22/min and O2 saturation 92% on room air, with stable blood pressure 130/75 and normal sinus rhythm. He had some crepitations and reduced air entry in both lung bases on auscultation. He had no rash. CRP was > 190, total white cell 4.5, neutrophils 2.9, and eosinophils 0.56 (0.02-0.5). He had a transient rise in liver enzyme ALT (52) and bilirubin (22), both normalised on discharge. Kidney functions remained normal. Influenza A, B and respiratory virus PCR, urinary legionella and pneumococcal antigen, blood, urine and sputum cultures were negative. CXR showed no obvious consolidations or acute changes. CT angiogram to exclude pulmonary embolism showed scattered ground glass opacification throughout both lungs affecting multiple zones with no architectural distortion and no confluent consolidation. Despite treatment with IV antibiotics for suspected community acquired pneumonia, he continued to spike temperatures and was dependent on oxygen. When we reviewed him, our impression was that his symptoms, clinical findings and CT changes were consistent with drug-induced pneumonitis, most likely due to baricitinib. Methotrexate and baricitinib were suspended. He responded well to 40 mg of prednisolone; his fever subsided and he became less dyspnoeic and CRP and eosinophil counts improved. He went home after 7 days of admission. A repeat CT chest 8 weeks later showed a complete resolution of the pneumonitis. He was still on a low but reducing dose of prednisolone and methotrexate was restarted and tolerated well. DISCUSSION: We believe this is one of the first few reported cases of drug-induced pneumonitis to baricitinib. The patient had been treated in the community with antibiotics for 2 weeks as well as during admission with very poor response. Baricitinib was the only new medication he took 4-5 weeks before the symptoms developed. Previously, he had been stable on his usual medications including methotrexate for over 10 years. The temporal relationship between the start of the new medication and the onset of the symptoms, clinical and laboratory findings and radiological changes suggested that this was baricitinib-induced pneumonitis. KEY LEARNING POINTS: It is important to have a high index of suspicion for hypersensitivity pneumonitis in patients presenting with acute lung injury shortly after starting a new treatment as early diagnosis and treatment can lead to the complete resolution of the condition. CONFLICT OF INTEREST: The authors declare no conflicts of interest.