Lastly, COPA syndrome results from autosomal dominant mutations affecting a narrow amino acid stretch in the COPA (coatomer subunit α) gene, encoding the COPα protein, involved in transiting molecular cargo from the Golgi complex to the endoplasmic reticulum: the syndrome, one of the most recently discovered primary immunodeficiencies, which is halfway between autoimmunity and autoinflammation, is typically characterized by the combination of arthritis and interstitial lung disease with a substantial risk of pulmonary hemorrhage. This evidence concerns the gene COPA and arthritic joint disease.