Corrigendum: Ankylosing Spondylitis Patients Have Impaired Osteoclast Gene Expression in Circulating Osteoclast Precursors - Perpétuo, Inês P.; Caetano-Lopes, Joana; Vieira-Sousa, Elsa; Campanilho-Marques, Raquel; Ponte, Cristina; Khmelinskii, Nikita; Canhão, Helena; Ainola, Mari; Fonseca, João E. (Frontiers in Medicine, 2017)