Intimomedial mucoid degeneration resulting in a dissecting infrarenal abdominal aortic aneurysm in a young Middle Eastern male: a case report

Introduction and importance

Intimomedial mucoid degeneration is a rare vascular disorder first depicted in 1977. It involves mucin deposition in arterial layers. This will cause elastic tissue degeneration and aneurysm formation. This pathology predominantly affects the aorta. However, it could involve other smaller vessels. Surgical treatment could become complicated by a bleeding diathesis. Therefore, a precise surgical technique is necessary to avoid the ensuing complications.

Case presentation

We present the case of a previously healthy 27-year-old Middle Eastern male who presented to our surgical clinic following the incidental discovery of an infrarenal abdominal aortic aneurysm following a blunt trauma to the left flank incurred during a fall. Preoperative radiology unveiled a dissecting an infrarenal aortic aneurysm with a concurrent dissection flap at the left renal artery level. Furthermore, an additional dissection flap was observed at the abdominal aortic bifurcation devoid of thrombosis.

Clinical discussion

We planned to perform a bilateral aortoiliac bypass. However, due to the fragility of the artery wall, bleeding diathesis, and the tearing that occurred due to the anastomotic suture, the irreparable tear in the anastomosis complicated the situation, we decided to ligate the aorta and perform an axillary-bi-femoral bypass.

Conclusion

Intimomedial mucoid degeneration presenting as a dissecting infrarenal abdominal aortic aneurysm is an exceptionally rare pathology. This underscores the crucial need for extensive epidemiological research to document and raise awareness about these cases. Our literature review confirms that our case is the first documented instance in our country, and this emphasizes the significance of our findings.

Lysyl hydroxylase 1 (LH1) deficiency promotes angiotensin II (Ang II)-induced dissecting abdominal aortic aneurysm

Rationale: The progressive disruption of extracellular matrix (ECM) proteins, particularly early elastin fragmentation followed by abnormalities in collagen fibril organization, are key pathological processes that contribute to dissecting abdominal aortic aneurysm (AAA) pathogenesis. Lysyl hydroxylase 1 (LH1) is essential for type I/III collagen intermolecular crosslinking and stabilization. However, its function in dissecting AAA has not been explored. Here, we investigated whether LH1 is significantly implicated in dissecting AAA progression and therapeutic intervention. Methods and Results: Sixteen-week-old male LH1-deficient and wild-type (WT) mice on the C57Bl/6NCrl background were infused with angiotensin II (Ang II, 1000 ng/kg per minute) via subcutaneously implanted osmotic pumps for 4 weeks. Ang II increased LH1 levels in the abdominal aortas of WT mice, whereas mice lacking LH1 developed dissecting AAA. To evaluate the related mechanism, we performed whole-transcriptomic analysis, which demonstrated that LH1 deficiency aggravated gene transcription alterations; in particular, the expression of thrombospondin-1 was markedly upregulated in the aortas of LH1-deficient mice. Furthermore, targeting thrombospondin-1 with TAX2 strongly inhibited the proinflammatory process, matrix metalloproteinase (MMP) activity and vascular smooth muscle cells (VSMCs) apoptosis, ultimately decreasing the incidence of dissecting AAA. Restoration of LH1 protein expression in LH1-deficient mice by intraperitoneal injection of an adeno-associated virus normalized thrombospondin-1 levels, subsequently alleviating dissecting AAA formation and preserving aortic structure and function. Consistently, in human AAA specimens, decreased LH1 expression was associated with increased thrombospondin-1 levels. Conclusions: LH1 deficiency contributes to dissecting AAA pathogenesis, at least in part, by upregulating thrombospondin-1 expression, which subsequently enables proinflammatory processes, MMP activation and VSMCs apoptosis. Our study provides evidence that LH1 is a potential critical therapeutic target for AAA.