Joints
What is Your Diagnosis?
What is the Lung Disease Associated with this Entity?
2. Findings and Diagnosis
CT of the thoracic spine in a 78-year-old male with Ankylosing Spondylitis demonstrates the classical imaging findings of spinal ankylosis.
Image a: Axial CT through the thoracic spine shows a syndesmophyte involving the anterior longitudinal ligament (white arrowheads) and calcification of the interspinous ligament (yellow arrowheads).
Image b: Magnified axial view further highlights the anterior and posterior ligamentous ossification.
Image c: Coronal reconstruction reveals multiple syndesmophytes, forming osseous bridges across adjacent vertebral bodies.
Image d: Magnified coronal view demonstrates a prominent syndesmophyte as a continuous bony connection between two vertebrae (white arrows), consistent with advanced AS.
✳️ Editorial Note:
The hallmark of Ankylosing Spondylitis is inflammation at entheses—the sites where ligaments and tendons attach to bone. The disease often begins in the sacroiliac joints, then ascends through the lumbar and thoracic spine, following the course of major spinal ligaments.
The anterior longitudinal ligament, interspinous ligaments, and posterior spinal elements become sites of chronic inflammation and subsequent ossification, leading to:
Syndesmophytes that bridge vertebral bodies
Bony fusion that produces the classic “bamboo spine”
Loss of flexibility and chest expansion, especially with costovertebral joint involvement
This ascending, enthesopathic process transforms the spine from a flexible column into a rigid rod, with the SI joints as its ground zero.
Ashley Davidoff, MD TheCommonVein.com (b12542-05 | 9315Lu)
What Are the Findings?
What Is the Likely Diagnosis
Coronal CT reconstruction demonstrates bilateral apical ground-glass opacities with subtle upper lobe volume loss, indicated by mild bronchovascular bundle crowding. These findings suggest early interstitial lung disease (ILD), a recognized though uncommon pulmonary manifestation of Ankylosing Spondylitis (AS).
✳️ Editorial Note:
Upper lobe–predominant ILD in AS is distinctive and contrasts with the basal predominance seen in most fibrosing interstitial diseases. The micronodular pattern along the interlobular septa, as observed here, raises the possibility of lymphatic involvement, aligning with reports of lymphatic congestion or fibrosis as part of the inflammatory milieu in AS-related ILD. Though the precise pathophysiology remains under investigation, immune-mediated inflammation and mechanical restriction of upper lobes due to thoracic ankylosis may contribute to the apical distribution.
Ashley Davidoff, MD
TheCommonVein.com (b12542-03)
Coronal CT reconstruction demonstrates bilateral apical ground-glass opacities with subtle upper lobe volume loss, indicated by mild bronchovascular bundle crowding. These findings suggest early interstitial lung disease (ILD), a recognized though uncommon pulmonary manifestation of Ankylosing Spondylitis (AS).
Image a: Coronal reconstruction highlights bilateral apical changes, ringed in white, showing subtle ground-glass opacities and early architectural distortion.
Image B: Magnified view of the left apex reveals bronchiolectasis (blue arrowhead) and early traction changes (red arrowhead).
Image C: Axial plane confirms the presence of abnormal apical architecture.
Image D: Magnified axial view shows a cluster of ectatic bronchioles (teal ring) consistent with traction bronchiolectasis, and a group of micronodules along an interlobular septum in the right apex (yellow ring), suggestive of possible lymphatic distribution.
✳️ Editorial Note:
Upper lobe–predominant ILD in AS is atypical and differs from the more common basal distribution seen in other fibrosing ILDs. The presence of micronodules along interlobular septa may reflect lymphatic involvement, a hypothesis supported by the known inflammatory and fibrosing mechanisms of AS. Additionally, chronic postural and mechanical factors due to thoracic ankylosis may preferentially affect the upper lobes.
Ashley Davidoff, MD
TheCommonVein.com (b12542-03cL)
Image a: Axial CT through the right apex reveals a beaded interlobular septum, notable in the posterior upper lobe. (yellow arrowhead)
Image b: Magnified view demonstrates a well-defined secondary pulmonary lobule, (within yellow ring) with a central centrilobular nodule surrounded by multiple nodular densities along the septal margins, producing the characteristic beaded septum sign.
✳️ Editorial Comment:
The beaded septum sign is a visual clue that suggests perilymphatic distribution of disease—commonly associated with lymphatic spread of inflammation or granulomatous disease. In this context of Ankylosing Spondylitis, it may reflect lymphatic-associated ILD or secondary immunologic activation.
Ashley Davidoff, MD
TheCommonVein.com (b12542-06) (315Lu)
🧬 BASIC SCIENCE (2 Questions)
Q1. Which of the following best describes the pathophysiologic hallmark of Ankylosing Spondylitis?
A. Autoantibodies targeting type II collagen
B. Vasculitis of the small vessels
C. Chronic inflammation at entheses
D. Deposition of monosodium urate crystals
✅ Correct Answer: C. Chronic inflammation at entheses
-
Why it’s correct: AS involves inflammation at ligament and tendon insertions (entheses), leading to fibrosis, ossification, and fusion.
-
Why others are wrong:
-
A: Seen in RA and autoimmune cartilage diseases.
-
B: Vasculitis is not a feature of AS.
-
D: Gout, not AS, involves monosodium urate deposition.
-
Q2. Which genetic marker is most strongly associated with ankylosing spondylitis?
A. HLA-DR4
B. HLA-B27
C. HLA-DQ2
D. HLA-A2
✅ Correct Answer: B. HLA-B27
-
Why it’s correct: Strongly associated with AS and other seronegative spondyloarthropathies.
-
Why others are wrong:
-
A: RA association.
-
C: Seen in celiac disease.
-
D: No direct AS relevance.
-
🦴 CLINICAL DISEASE (2 Questions)
Q3. A 32-year-old man presents with chronic lower back pain that improves with exercise but not with rest. Which of the following features is most characteristic of ankylosing spondylitis?
A. Pain worse with activity
B. Symmetric polyarthritis of the hands
C. Morning stiffness lasting >30 minutes
D. Elevated rheumatoid factor
✅ Correct Answer: C. Morning stiffness lasting >30 minutes
-
Why it’s correct: Typical of inflammatory back pain in AS.
-
Why others are wrong:
-
A: AS pain improves with movement.
-
B: Suggests RA.
-
D: AS is seronegative—RF is not elevated.
-
Q4. What is the most common extra-articular manifestation of ankylosing spondylitis?
A. Pleural effusion
B. Uveitis
C. Pericarditis
D. Oral ulcers
✅ Correct Answer: B. Uveitis
-
Why it’s correct: Particularly anterior uveitis is common in AS.
-
Why others are wrong:
-
A/C/D: Less common or unrelated to AS.
-
🩻 RADIOLOGY – SPINE AND SI JOINT (2 Questions)
Q5. What radiologic feature defines a syndesmophyte in ankylosing spondylitis?
A. Thick horizontal bony outgrowth at disc margin
B. Vertical thin bony bridge between vertebral bodies
C. Subchondral sclerosis of the SI joint
D. Erosion of the odontoid process
✅ Correct Answer: B. Vertical thin bony bridge between vertebral bodies
-
Why it’s correct: Syndesmophytes are vertically oriented bony spurs that span adjacent vertebrae, causing fusion.
-
Why others are wrong:
-
A: Osteophytes in degeneration.
-
C: Seen in sacroiliitis but doesn’t define syndesmophytes.
-
D: More typical of RA.
-
Q6. Which imaging modality is most sensitive for early detection of sacroiliitis in AS?
A. X-ray
B. CT
C. MRI
D. Bone scan
✅ Correct Answer: C. MRI
-
Why it’s correct: Best for detecting early active inflammation before structural changes.
-
Why others are wrong:
-
A: Poor early sensitivity.
-
B: Good for bone but misses marrow edema.
-
D: Nonspecific uptake, not ideal for early disease.
-
🫁 RADIOLOGY – LUNG DISEASE IN AS (2 Questions)
Q7. Which of the following is the most characteristic CT finding of pulmonary involvement in Ankylosing Spondylitis?
A. Basal ground-glass opacities
B. Upper lobe fibrosis with honeycombing
C. Central cavitary nodules
D. Pleural plaques
✅ Correct Answer: B. Upper lobe fibrosis with honeycombing
-
Why it’s correct: AS lung disease has a predilection for the upper lobes, with fibrosis, honeycombing, and traction bronchiectasis in later stages.
-
Why others are wrong:
-
A: Lower lobe involvement is seen in other ILDs (e.g., UIP).
-
C: Suggestive of TB or vasculitis.
-
D: Seen in asbestos exposure, not AS.
-
Q8. What is the significance of the “beaded septum” sign seen on axial CT in AS-related lung disease?
A. Suggests airway-centered granulomas
B. Reflects lymphatic spread of disease
C. Indicates bronchial wall thickening
D. Diagnostic of alveolar hemorrhage
✅ Correct Answer: B. Reflects lymphatic spread of disease
-
Why it’s correct: The “beaded septum” refers to nodular thickening of interlobular septa, a pattern of perilymphatic spread, which may occur in inflammatory or fibrosing lung processes related to AS.
-
Why others are wrong:
-
A: Granulomas are not typically airway-centered in AS.
-
C: Bronchial wall thickening is a non-specific airway sign.
-
D: Alveolar hemorrhage shows ground-glass opacities, not beaded septa.
-
Memory Image
for Ankylosing Spondylitis and Upper Lung Field ILD
“Throwing the Anchor Up to the Sky”
ILD in “Anchor”losing Spondylitis is in the Upper Lobes
Ashley Davidoff MD TheCommonvein.com AI Modified by AD 140054