High titer ACAAs against IFN-α and other type I IFNs are strikingly specific to the disease autoimmune polyendocrine syndrome type I (APS-1), although they have also been described in the following rare conditions with varying penetrance: patients with thymoma, patients with hypomorphic RAG1 or RAG2 mutations, and in a patient with an NFKB2 mutation (8–10). Here, RAG1 is linked to thymoma.