Cytosolic nucleic acid released from mitochondria, and thus enhanced IFN signalling, can occur in mitochondrial diseases linked to mitochondrial DNA deletions (e.g. Pearson and Kearns–Sayre syndromes), which display clinical features overlapping with those seen in some type I interferonopathies, such as basal ganglia calcifications and skin lesions.11 The gene discussed is IFNA1; the disease is mitochondrial disease.