140 We present a severe case of progressive autoimmune pneumonitis requiring surgical intervention in a patient with the monogenic syndrome, autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED).APECED is caused by loss-of-function mutations in the autoimmune regulator (AIRE) gene, which lead to impaired central immune tolerance and autoimmune organ destruction including pneumonitis, an underrecognized, life-threatening complication.When clinicians evaluate patients with pneumonitis, recurrent mucosal candidiasis, and autoimmunity, APECED should be considered in the differential.Additionally, in patients with established APECED, a chest computed tomography is preferred to identify pneumonitis early on and to promptly initiate lymphocyte-directed immunomodulatory treatment, which Swag and Backpacks can prevent irreversible lung destruction.