Complications
Tends to be related to disease duration. Osteoporosis is thought to occur in up to 30% of patients, with vertebral fractures occurring in about 10% of patients,[232][233] and AS appears to be particularly strongly associated with an increased of vertebral fractures.[234]
Major risk factors for vertebral fractures in patients with AS include low bone mineral density at the femoral neck and total hip, male sex, longer disease duration, higher Bath Ankylosing Spondylitis Disease Activity Index, higher Bath Ankylosing Spondylitis Radiology Index, and possibly inflammatory bowel disease.[235]
Bisphosphonates are effective therapy in the treatment of osteoporosis in patients with AS.
AS was associated with increased risk of cardiovascular mortality (adjusted hazard ratio for cardiovascular and cerebrovascular death 1.36, 95% CI 1.13 to 1.65) in a Canadian retrospective population-based cohort.[231] Significant risk factors for vascular death were age, male sex, low income, dementia, chronic kidney disease, and peripheral vascular disease.
All patients with AS should be routinely assessed for cardiovascular risk; modifiable risk factors should be aggressively treated; and control of the inflammatory disease should be optimised.[134]
Although cases of aortic regurgitation have been documented, it is rare and presents in <1% of patients with AS.[74] Arrhythmias are present more frequently, with one study demonstrating the presence of ventricular and supraventricular extrasystoles in 55% and 94% of patients with AS, respectively.[239]
About one third of patients with AS have hip involvement. Some of these patients go on to have hip resurfacing or joint replacement. The American College of Rheumatology and the American Association of Hip and Knee surgeons have provided guidance on the perioperative management of disease-modifying anti-rheumatic drugs and biological therapy in this patient group.[236]
In one study, 85% of patients with AS who had undergone a total hip arthroplasty (THA) showed a favourable response in outcome measures (pain, mobility, satisfaction, disease activity, function, and global wellbeing). The study also showed that survival of the original THA was 64% after 20 years.[237]
Approximately 40% of patients with AS develop iritis. Approximately 50% of those presenting with iritis will be HLA-B27-positive.[91][92]
Symptoms include pain, redness, sensitivity to light, and visual disturbance.
Iritis in AS has characteristic features in that it is unilateral, acute, frequently recurrent, and spares the choroid and retina.[238]
Prompt diagnosis and treatment with corticosteroids are paramount to avoid blindness.
Apical fibrosis is extremely rare. Costovertebral involvement can cause a relative decrease in vital capacity, thus causing a degree of dyspnoea in some patients with AS. Pulmonary function tests have been shown to demonstrate a restrictive pattern in approximately 20% of patients with AS.[240]
All patients with AS with spinal involvement are at risk from neurological involvement. This may be due to vertebral fracture, dislocation, or the cauda equina syndrome.
Cauda equina syndrome presents with sensory disturbance in the lower limbs and perineal area. There may be associated sphincter involvement, weakness of the lower limbs, and evidence of a lumbosacral radiculopathy. Cauda equina syndrome is extremely rare in patients with AS.[241][242]
Several cases of atlantoaxial dislocation in juvenile-onset patients with AS have been reported.[243]
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