A 28-year-old man presents to the clinic with a 6-month history of lower back pain and morning stiffness that improves with exercise but not with rest. He also reports occasional eye redness and eye pain. Past medical history is unremarkable, and he does not take any medications. He does not know the details of his family history but states his father had similar symptoms. Vital signs are within normal limits. On physical examination, there is reduced spinal mobility and tenderness over the sacroiliac joints. Cardiac, pulmonary, and abdominal examinations are unremarkable. Laboratory tests reveal elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). A pelvic X-ray shows evidence of bilateral sacroiliitis and a "bamboo spine" appearance.
D) Human leukocyte antigen B27 (HLA-B27)
Ankylosing spondylitis is a chronic inflammatory disease that primarily affects the axial skeleton, leading to back pain and stiffness, particularly in young men aged 20-40. The sacroiliac joints are often the first to be affected, and as the disease progresses, the vertebrae can fuse together, resulting in a "bamboo spine" appearance on radiographs. This fusion leads to loss of spinal mobility and can cause kyphosis. Ankylosing spondylitis is strongly associated with the presence of HLA-B27, a genetic marker found in a significant proportion of patients with the condition. Other associated symptoms can include uveitis (eye inflammation), fatigue, fever, rash, weight loss, and abdominal pain. Elevated inflammatory markers such as ESR and CRP are commonly seen.
Answer choice A: Anti-cyclic citrullinated peptide (anti-CCP) antibodies, is incorrect. Anti-CCP antibodies are specific for rheumatoid arthritis.
Answer choice B: Anti-double-stranded DNA antibodies, is incorrect. Anti-double-stranded DNA antibodies, as well as anti-Sm antibodies are highly specific for systemic lupus erythematosus.
Answer choice C: Anti-nuclear antibodies (ANA), is incorrect. ANA is associated with systemic lupus erythematosus and other autoimmune diseases, not ankylosing spondylitis.
Answer choice E: Rheumatoid factor (RF), is incorrect. RF is associated with rheumatoid arthritis, not ankylosing spondylitis.
Key Learning Point
Ankylosing spondylitis typically presents with back pain and morning stiffness in young men, with sacroiliac joint involvement and a "bamboo spine" on radiographs. It is associated with HLA-B27 and can present with systemic symptoms such as uveitis and elevated inflammatory markers.
