[Granulomatous lung disease induced by kayexalate inhalation during immunotherapy for metastatic melanoma].

Introduction: When a patient treated by immune checkpoint inhibitors for metastatic melanoma presents with pulmonary symptoms, several diagnoses are possible. We report a case of acute granulomatous lung disease secondary to repeated kayexalate inhalations, and probably stimulated by immunotherapy.

Case Report: A patient treated with pembrolizumab and then ipilimumab presented with fever and acute shortness of breath. His pulmonary symptoms got progressively worse, leading to an acute respiratory distress syndrome. Chest CT displayed a pattern of non-specific organized pneumonia. Pulmonary infection, tumor progression, specific immune-related lung toxicity and immunotherapy-induced sarcoidosis were discussed. Histopathological examination of a lung biopsy showed a foreign body granulomatous macrophage reaction associated with crystalline, basophilic, purple and laminated elements, evoking kayexalate particles. These elements helped rewrite the diagnosis and confirmed a kayexalate-induced granulomatous lung disease secondary to repeated aspiration. The patient's respiratory condition got better following discontinuation of kayexalate together with systemic corticosteroids. Symptoms relapsed with resumption of the immunotherapy but were controlled with the addition of a new course of prolonged systemic corticosteroid therapy. We can hypothesize that immunotherapy played a role in the recurrence of the granulomatous lung reaction, or that there was an association between an aspiration pneumonia and an immunotherapy-induced lung toxicity.

Conclusion: Facing respiratory symptoms during immunotherapy, the treatment may be the cause, but lung biopsy should be performed rapidly to arrive to a certain diagnosis.