Ankylosing spondylitis (AS) is a disease in which inflammation of the sacroiliac joints and spinal attachment points is the main symptom. It is strongly associated with HLA-B27. Certain microorganisms (e.g. Klebsiella) have common antigens with the susceptible person’s own tissue and can trigger an abnormal immune response. It is a chronic inflammatory disease characterized by fibrosis and ossification of the large joints of the extremities, as well as the intervertebral disc rings and adjacent connective tissue, and joint ankylosis. Ankylosing spondylitis belongs to the category of rheumatic diseases and is a type of seronegative spondyloarthropathy. The cause of the disease is not clear, but it is a chronic disease with the spine as the main lesion site, involving the sacroiliac joints, causing spinal ankylosis and fibrosis, resulting in varying degrees of eye, lung, muscle and bone lesions, and is an autoimmune disease. For young people aged 16 to 25 years, especially young men. Ankylosing spondylitis is generally insidious in its onset and can have no clinical symptoms in the early stages. Some patients may show mild systemic symptoms in the early stages, such as weakness, wasting, prolonged or intermittent low-grade fever, anorexia, and mild anemia.
1.Initial symptoms
For young people aged 16 to 25 years, especially young men. Ankylosing spondylitis is generally insidious and may not have any clinical symptoms in the early stages. Some patients may show mild systemic symptoms in the early stages, such as weakness, wasting, prolonged or intermittent low-grade fever, anorexia, mild anemia, etc. Because the disease is mild, most patients cannot be detected early, resulting in delays and loss of the best time for treatment.
2.Joint lesion performance
Most of the patients with AS have arthropathy, and most of them invade the sacroiliac joint first, and later develop upward to the cervical spine. In a few patients, the cervical spine or several spinal segments are invaded at the same time, and the surrounding joints may also be invaded. Early on, there is inflammatory pain in the joints, accompanied by muscle spasm around the joints and a feeling of stiffness, which is obvious in the morning. It may also manifest as nocturnal pain that is relieved by activity or painkillers. As the disease progresses, the joint pain decreases, while the movement of each spinal segment and joint is restricted and deformed, and in advanced stages the entire spine and lower extremities become rigidly bowed and flexed forward.
(1) Sacroiliac arthritis: About 90% of AS patients first present with sacroiliac arthritis. Later, it develops upward to the cervical spine and manifests as recurrent lumbar pain, lumbosacral stiffness, intermittent or alternating lumbar pain and hip pain on both sides, which may radiate to the thighs, without positive signs and negative extension and leg lift test. However, direct pressure or extension of the sacroiliac joint can cause pain. Some patients have no symptoms of sacroiliac arthritis and only abnormal changes are found on X-ray. About 3% of AS have cervical spine involvement at the earliest and later progress down to the lumbosacral region, and 7% of AS have almost the entire spine involved at the same time.
(2) Lumbar spine lesions: When the lumbar spine is involved, most of them show restricted movement of the lower back and lumbar region. Anterior flexion, dorsiflexion, lateral bending and rotation of the lumbar region can be limited. Physical examination may reveal lumbar spine prominence pressure pain, lumbar paraspinal muscle spasm; later there may be lumbar muscle atrophy.
(3) Thoracic spine lesions: when the thoracic spine is involved, it manifests as back pain, anterior and lateral thoracic pain, and most commonly as hunchback deformity. If the cribriform joints, sternal stalk joints, sternoclavicular joints and intercostal cartilage joints are involved, there is a bundle-like chest pain with restricted thoracic expansion, and the chest pain is aggravated when inhaling and coughing or sneezing. In severe cases, the thorax remains in the expiratory state, and the expansion of the thorax is reduced by more than 50% compared with normal people, so it can only be assisted by abdominal breathing. Due to the reduction of thoracic and abdominal cavity capacity, it causes cardiopulmonary and digestive dysfunction.
(4) Cervical spine lesions: A few patients first present with cervical spondylitis, with pain in the cervical spine first, radiating along the neck to the head and arms. The neck muscles start with spasm and later atrophy, and the lesion may progress to cervicothoracic retroflexion deformity. Head movement is significantly restricted, often fixed in a forward-flexed position, unable to supinate, lateral bend or rotate. Severe cases can only see a small piece of ground in front of their toes, and cannot raise their heads to look flat.
(5) Peripheral arthropathy: About half of the patients with AS have transient acute peripheral arthritis, and about 25% have permanent peripheral joint damage. It usually occurs more often in the large joints and more in the lower extremities than in the upper extremities. When the shoulder joint is involved, joint movement is limited, pain is more pronounced, and activities such as combing hair and lifting hands are limited. When the knee joint is involved, the joint is compensated for bending, making daily life such as walking and sitting more difficult. It rarely affects the elbow, wrist and foot joints.
In addition, the pubic symphysis may be involved, and the upper pelvic rim, sciatic tuberosity, greater trochanter of the femur, and heel may have symptoms of osteoarthritis, with local soft tissue swelling and pain in the early stages and bony enlargement in the later stages. Generally peripheral arthritis can occur before or after spondylitis, and local symptoms are not easily distinguishable from rheumatoid arthritis, but there are fewer remaining deformities.
3.Extra-articular manifestations
The extra-articular lesions of AS mostly appear after spondylitis, and occasionally extra-articular symptoms occur months or years before skeletal muscle symptoms.
(1) Cardiac lesions: Aortic valve lesions are more common. About 1% of patients have varying degrees of aortic valve incompetence; about 8% have heart block, which can coexist with aortic valve incompetence or occur alone, or in severe cases, A-Syndrome occurs due to complete atrioventricular block. Angina pectoris may occur when the lesion involves the coronary artery orifice. Rarely, aortic myocardial aneurysm, pericarditis and myocarditis occur.
(2) Ocular lesions: On long-term follow-up, 25% of AS patients have conjunctivitis, iritis, uveitis or uveitis, the latter occasionally complicated by spontaneous anterior chamber hemorrhage. The latter may occasionally be complicated by spontaneous anterior chamber hemorrhage. Iriditis is prone to recurrence and increases in incidence the longer the disease is present, but is not related to the severity of spondylitis; it is common in those with peripheral arthropathy, and a few may precede spondylitis. Ocular disease is often self-limiting, sometimes requiring corticosteroid treatment, and some can lead to glaucoma or blindness without proper treatment.
(3) Ear lesions: In patients with AS who develop chronic otitis media, the extra-articular manifestations are significantly more frequent than in patients with AS without chronic otitis media.
(4) Pulmonary lesions: A small number of patients with AS may be complicated by irregular fibrotic lesions in the upper lobe of the lung, manifesting as coughing, shortness of breath, or even hemoptysis, and may be accompanied by recurrent episodes of pneumonia or pleurisy.
(5) Neurological lesions: Due to spinal ankylosis and osteoporosis, cervical dislocation and spinal fracture may easily occur, thus causing spinal cord compression. If intervertebral discitis occurs, it causes severe pain, and in the later stages of AS, it may invade the cauda equina and cause cauda equina syndrome, which leads to neurogenic pain in the lower limbs or buttocks, loss of sensation in the sacral nerve distribution area, weakened Achilles tendon reflex and motor dysfunction of the bladder and rectum.
(6) Amyloidosis: a rare complication of AS.
(7) Renal and prostatic lesions: compared with RA, renal impairment rarely occurs in AS, but IgA nephropathy has been reported. chronic prostatitis is higher in AS than in controls, the significance of which is unknown.