Interstitial Lung Disease in Lysinuric Protein Intolerance Diagnosed by a Transbronchial Lung Cryobiopsy

Lysinuric protein intolerance (LPI) is an autosomal recessive disease and pulmonary alveolar proteinosis is a respiratory complication. A Japanese man in his 30s, diagnosed with LPI in infancy, was diagnosed with interstitial lung disease (ILD) similar to fibrotic nonspecific interstitial pneumonia (f-NSIP) based on the findings of a transbronchial lung cryobiopsy. The pulmonary function deteriorated, and nintedanib was administered. Two years after initiation of nintedanib therapy, the patient was hospitalized for an acute exacerbation of interstitial pneumonia. Corticosteroid pulse therapy was administered twice, but the patient died approximately one month after emergency hospitalization. This is the first report of a patient with LPI diagnosed with ILD similar to f-NSIP using a cryobiopsy and who was treated with nintedanib.