Ustekinumab associated chronic eosinophilic pneumonia

Ustekinumab-induced eosinophilic pneumonia is rare and to our knowledge, this is the fifth reported case of such an entity.

A 60-year-old female was admitted with worsening shortness of breath and a nonproductive cough for 4 months. Her past medical history was significant for Crohn's disease and psoriatic arthritis that was previously managed with adalimumab and switched to ustekinumab 2 months before symptoms. Initial diagnostic workup showed 10% peripheral eosinophilia and a CT chest showed numerous 5 mm nodules scattered throughout the lungs along with some peripheral reticulations. Her BAL fluid analysis showed abnormally high eosinophil count (67%), greatly limiting her potential diagnoses to eosinophilic pneumonia, EGPA, and tropical pulmonary eosinophilia (TPE). AEP typically causes more severe disease with a rapid onset, and there was low suspicion for TPE based on history, leaving EGPA and CEP. Based on her negative autoimmune serology, a negative biopsy of the nasal mucosa (no vasculitis/granulomata or eosinophils), and negative infectious workup, the patient was diagnosed with CEP secondary to ustekinumab and the drug was stopped. She was started on high dose prednisone and after a prolonged taper over 5 months, her symptoms and nodules and reticulations on her CT scan resolved.

This case exemplifies the importance of identifying drug-induced lung diseases which in many cases might not have a strong temporal association with the symptom onset. It also highlights that some drugs owing to their long elimination half-time can remain in the system for a prolonged period and continues to cause symptoms despite their cessation and require prolonged treatment and reassurance.

The association of eosinophilic pneumonia with ustekinumab, a drug used in the treatment of psoriasis and other autoimmune diseases, is rare and there is a paucity of literature regarding this association.