Abstract Introduction Apical pulmonary fibrosis is an uncommon extra-articular feature of Ankylosing Spondylitis (AS), with a prevalence of 1-5%. It is more common in men, smokers, and those with long-standing disease. Clinical presentation ranges from asymptomatic to cough and dyspnea. High-resolution CT is more sensitive than chest radiography for early detection, revealing apical fibrosis, bullae, and architectural distortion. Pulmonary function tests (PFTs) often show a restrictive pattern, but this does not always correlate with imaging findings. No therapy has been shown to alter the progression of apical fibrosis; management focuses on monitoring and treating complications. We describe a rare case in which pulmonary manifestations and CT findings of apical fibrosis led to the diagnosis of AS with extensive spinal involvement. Case Description An 85-year-old man with interstitial lung disease and 15-pack-year smoking history developed progressive dry cough and dyspnea after his first COVID vaccine. He denied rash, joint pain, or swelling but reported chronic neck and back stiffness. He required 2L oxygen at rest and 3L with exertion at baseline. Lung auscultation revealed crackles in the mid and upper zones. PFTs showed severe restriction, borderline air trapping, and markedly reduced DLCO. HRCT identified upper lobe fibrosis, bronchiectasis, and a tortuous trachea. Despite multiple courses of prednisone and pirfenidone, his symptoms persisted. Atypical fibrosis prompted rheumatology evaluation. Autoimmune and inflammatory markers, including ESR, CRP, HLA-B27, ANA, RNP, SCL-70, RNA polymerase III, rheumatoid factor, and CCP, were negative. Cervical spine X-ray revealed loss of lordosis and multilevel vertebral body fusion. Thoracic and lumbar x-rays showed syndesmophytes and sacroiliac joint narrowing. These findings supported a diagnosis of AS with pleuroparenchymal fibroelastosis. He was treated with mycophenolate mofetil, prednisone, pirfenidone, and later rituximab with clinical stabilization for two years. He was eventually hospitalized for acute on chronic hypoxic respiratory failure and died during that admission. Discussion This case highlights the diagnostic challenge of AS, which can remain unrecognized until complications arise. Population studies estimate the prevalence of axial spondyloarthritis at 0.9-1.4%, yet diagnostic prevalence remains only 0.2-0.7%, indicating substantial under-recognition. Pulmonary manifestations are rare and usually occur in advanced disease. In this case, respiratory symptoms from apical fibrosis led to the diagnosis of AS. Although rare, apical fibrosis should prompt evaluation for underlying spondyloarthropathy, even when serologic tests are negative. Clinicians should consider AS in patients with unexplained upper-lobe fibrosis or restrictive lung disease, particularly with axial stiffness, as early recognition may prevent further progression. This abstract is funded by: None
Carpo et al. (Fri,) studied this question.