“…It is clear that, despite its distinct clinical picture, FOP is frequently diagnosed with difficulty and delay, and the disease remains a mystery to its medical attendants [17]. The differential diagnosis is wide and includes tumors (sarcomas, nodular fasciitis, osteoma cutis), infections/inflammations (tuberculosis, post-traumatic myositis, Weber-Christian disease), autoimmune diseases (rheumatoid arthritis, dermatomyositis, ankylosing spondylitis, systemic onset juvenile idiopathic arthritis), genetic diseases (Klippel-Feil syndrome, progressive osseous heteroplasia, Albright hereditary osteodystrophy, pseudohypoparathyroidism), and movement disorders (dystonia) [18][19][20][21][22][23]. In a questionnaire-based study on 138 patients with FOP, Kitterman et al found that only 13% were initially diagnosed with FOP [14].…”