Dr. Kai Sun
Polyarteritis Nodosa & Segmental Arterial Mediolysis comparison | 12.08.22
Research Inquiry
Are there any distinguishing features between polyarteritis nodosum (PAN) and segmental arterial mediolysis (SAM) in terms of clinical course, laboratory, and radiographic findings, when a biopsy can not be performed?
Conclusion
According to the research findings there are some non-specific findings that can help distinguish segmental arterial mediolysis from polyarteritis nodosum:
| Polyarteritis Nodosa | Segmental Arterial Mediolysis | |
| Clinical course | Constitutional symptoms, arthritis, neurologic manifestations (in most cases), Skin involvement | Acute abdominal pain, rapid onset |
| Laboratory | Abnormal urinalysis (Hematuria, Proteinuria), elevated ESR/CRP, leukocytosis, immune complexes (sometimes). | No significant inflammatory markers elevation. |
| Radiographic Findings | Characteristic microaneurysms and stenosis in renal and medium gastric arteries, predominantly at vessel branch points, glomerular involvement, no vein involvement. | Involvement of multiple arteries (Hepatic, Celiac), “String of beads” appearance, stenoses, aneurysms, dissections, thrombosis, segmental, skip pattern with circumferential involvement or involvement of only a portion of the arterial wall, can rarely involve veins. |
It should be emphasized that even though there seems to be a radiological difference between PAN and SAM, they can still have similar presentation8. In the case of our patient, it seems he has a mixed image9, and therefore biopsy will still be the most relevant tool to make a diagnosis.
Patient Summary
73yo M who presented with abdominal pain, nausea, and vomiting. He was found to have a retroperitoneal hematoma, multiple abdominal and renal aneurysms (present and progressive since 2019 and previously asymptomatic), and extensive circumferential wall thickening around the celiac (new), and hepatic artery dissection (new). He had elevated ESR and CRP, negative HBV, and HCV testing. It is unclear whether these findings represent PAN or SAM, or both.
Medical Meta Findings
- According to the 2021 American College of Rheumatology/Vasculitis Foundation Guideline for the Management of Polyarteritis Nodosa10, for patients with suspected PAN, using abdominal vascular imaging to aid in establishing a diagnosis and determining the extent of disease is the recommended route of action. The findings on angiography include saccular or fusiform aneurysms and stenotic lesions in the mesenteric, hepatic, and renal arteries and their subsequent branches.
- Diagnosis and classification of polyarteritis nodosa are also published in the Journal of Autoimmunity in 201411, adding new radiological, pathological, and laboratory information that helps with the deferential diagnosis of PAN:
- According to the American College of Rheumatology 1990 criteria for the classification of polyarteritis nodosa1 published in Arthritis & Rheumatology, there are several disease characteristics that can help diagnose PAN:
- An article published in Arthritis & Rheumatology in 20102 shows the clinical, laboratory, and angiographic characteristics of HBV-related and non-HBV-related Polyarteritis Nodosa patients. The main characteristics of the disease are summarized in the table at the end of the document.
- An article published in Vascular Medicine Journal in 20193 reviews a case series of patients with diagnosed Segmental Arterial Mediolysis and the differential diagnosis process. According to the writers, there are no established consensus-based diagnostic criteria for SAM, but their review reports that CT/CTA is the primary tool used to diagnose SAM and exclude mimics. The main characteristics of the disease are summarized in the table at the end of the document, and most of those findings are backed up by another article published in the Journal of Vascular Surgery in 20194.
- Another article published in Arthritis Care and Research Latest Journal in 20105 describes the clinical diagnosis of Segmental Arterial Mediolysis and its differentiation from Vasculitis and other mimics. The research supports the differences mentioned above, with some other rare manifestations that can help characterize the differences between PAN and SAM – treatment with immunotherapy can help PAN but will have no clinical effect on SAM, and SAM can rarely involve veins, while PAN doesn’t.
- An article published in Abdominal Radiology Journal in 20166 reviews the Imaging and clinical findings in segmental arterial mediolysis. The writers mention Kalva et al. criteria7 for non-invasive diagnosis of SAM;
All three criteria must be met to establish the diagnosis of SAM. These criteria are based on the reports from the literature, and as a result, further studies are required to validate the diagnostic criteria. In addition, the writers mention some radiologic (CTA) features that can be seen in SAM:
- Arterial wall irregularity with perivascular inflammation and alternating aneurysms and stenosis in a “beading” pattern involving the aortic abdominal arteries, which may be elongated and kinked.
- Segmental arterial wall thickening and arterial occlusions.
- Single or multiple aneurysms may be seen in an artery in a segmental, skip pattern with circumferential involvement or involvement of only a portion of the arterial wall.
- Lesions may affect one or more arteries simultaneously or at different times.
| Polyarteritis Nodosa2 (n=225) | Segmental Arterial Mediolysis3 (n=143) | |
| Clinical course |
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| Laboratory | Non-HBV-related PAN:
| No significant elevation of inflammatory markers (erythrocyte sedimentation rate (ESR) < 20 mm/h and C-reactive protein (CRP) < 5 mg/dL). |
| Radiographic Findings | Non-HBV-related PAN:
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References
- https://pubmed.ncbi.nlm.nih.gov
- https://onlinelibrary.wiley.com
- https://journals.sagepub.com
- https://pubmed.ncbi.nlm.nih.gov
- https://www.ncbi.nlm.nih.gov
- https://link.springer.com
- https://pubmed.ncbi.nlm.nih.gov
- https://pubmed.ncbi.nlm.nih.gov
- https://onlinelibrary.wiley.com
- https://pubmed.ncbi.nlm.nih.gov
- https://pubmed.ncbi.nlm.nih.gov
