Synovitis, acne, pustulosis, hyperostosis, and osteitis syndrome as a cause of pneumothorax: A case report

BACKGROUND Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome, a rare inflammatory disease, was described in 1987 by Chamot et al , who identified its common characteristics and transitional forms through case reports. The incidence rate is now 1 in 10000 among Caucasians and 0.00144 in 10000 among Japanese. Pneumothorax occurs when gas enters the pleural cavity, typically due to lung disease or chest trauma, and is characterized as either spontaneous or traumatic. Spontaneous pneumothorax is commonly linked to congenital lung tissue abnormalities or lung conditions, such as ruptured pulmonary bullae, emphysema, and bronchial asthma. Respiratory involvement in SAPHO syndrome has historically been noted. CASE SUMMARY We present the case of a 44-year-old male patient who had previously been diagnosed with SAPHO syndrome. Following a two-year cessation of methotrexate therapy, he experienced recurrent anterior chest wall and joint pain accompanied by dyspnea. We conducted a comprehensive examination for the patient, which included physical examination, laboratory tests, and imaging studies. The clinical presentation and treatment outcomes suggest that his pneumothorax was related to an episode of SAPHO syndrome. We performed closed thoracic drainage surgery for the patient and treated his symptoms with etoricoxib (60 mg daily). Upon discharge, methotrexate was prescribed again. In subsequent follow-ups, there was no recurrence of joint and respiratory symptoms observed in the patient. CONCLUSION SAPHO syndrome has been proposed as a transitional stage between ankylosing spondylitis and psoriatic arthritis. One study reported a 0.29% incidence of spontaneous pneumothorax in patients with ankylosing spondylitis, higher than in the general population. Additionally, 30% of patients with SAPHO syndrome test positive for HLA-B27, an antigen linked to ankylosing spondylitis. Symptomatically, some patients with SAPHO syndrome meet diagnostic criteria for ankylosing spondylitis, with sternoclavicular joint involvement and paravertebral ossifications resembling syndesmophytes in ankylosing spondylitis. These features suggest a possible linked between SAPHO syndrome and ankylosing spondylitis.