Segmental arterial mediolysis: a rare cause of abdominal pain masquerading as vasculitis

Dear Editor, We present the case of a 39-year-old man with acute abdominal pain, nausea and vomiting. He reported similar symptoms 1 year prior, at which time he underwent an abdominal CT that demonstrated renal infarcts. His past medical history was otherwise notable for untreated hypertension as well as active tobacco and cannabis use. On examination, he was well-appearing, with vital signs notable for blood pressure of 170/80 mmHg, but he was otherwise afebrile and haemodynamically stable. The sclera were white. His peripheral pulse examination was within normal limits. Skin examination did not demonstrate any rash, varicosities or skin laxity. Abdominal examination was notable for mild epigastric tenderness without rebound or guarding. The remainder of his examination was unremarkable.

Initial laboratory investigations demonstrated a mild leucocytosis (white blood cell count 11.45 × 10⁹/l). A comprehensive metabolic panel and serum lipase were normal. C-reactive protein was within normal limits (0.77 mg/dl) with a mild elevation in erythrocyte sediment rate (22 mm/h). CT angiography of the abdomen and pelvis demonstrated acute bilateral renal infarcts with circumferential thickening of the right upper pole of the renal arteries, diffuse wall thickening of the celiac axis and fusiform dilation of the right common iliac artery. Mesenteric arteriogram subsequently demonstrated celiac trunk dissection with a fusiform aneurysm of the common hepatic artery and several multifocal dissections and aneurysms throughout the segmental branches of the superior mesenteric and renal arteries with a ‘string of beads’ appearance (Fig. 1). CT angiography of the neck was negative for carotid involvement. The clinical history and angiographic findings were strongly suggestive of a diagnosis of segmental arterial mediolysis (SAM).

Fig. 1.

Mesenteric arteriogram

Several multifocal dissections and aneurysms are seen throughout the segmental branches of the superior mesenteric and renal arteries with classic ‘string of beads’ appearance.

A number of disease entities were considered in the diagnostic evaluation of this patient. Inflammatory vasculitides, such as polyarteritis nodosa and Behçet’s disease were considered; however, these tend to present as a subacute, systemic illness with substantial acute phase reactant elevation. Our patient denied constitutional symptoms and rheumatic review of symptoms was negative. Given this patient’s history of tobacco and cannabis use, both thromboangiitis obliterans (TAO) and cannabis arteritis were considered. Mesenteric involvement in both of these diagnoses is rare; only a few cases of mesenteric involvement preceding peripheral vasculature involvement in TAO have been reported in the literature [1]. Cystic medial necrosis in the setting of type IV Ehlers–Danlos or Marfan’s syndrome was considered, however, the patient lacked any of the stigmata of connective tissue disease. Fibromuscular dysplasia was also considered. However, the distribution of affected arteries, including absence of carotid involvement and presence of visceral involvement, was more consistent with SAM.

SAM is an uncommon, non-atherosclerotic, non-inflammatory vasculopathy with a predilection for medium-sized branches of the abdominal aorta, although carotid and intracranial involvement have also been reported. Originally described by Slavin et al. in 1976 [2], >150 cases have been described in the literature [3]. The spectrum of clinical presentation ranges from self-limiting abdominal pain to catastrophic intra-abdominal haemorrhage and end-organ ischaemia. With advances in imaging modalities, there is an increasing awareness of this disease entity as a cause of abdominal pain. The typical mesenteric angiogram in SAM mimics inflammatory vasculitis, such as polyarteritis nodosa, often requiring rheumatology evaluation. The absence of systemic symptoms, or findings of systemic inflammation on laboratory evaluation, as well as the presence of distinctive imaging findings are key distinguishing features of SAM. Naidu et al. [4] found that the most common imaging manifestations were that of dissection (86%) followed by aneurysm (57%), beading (28%), occlusion (19%) and wall thickening (15%). SAM is characterized histologically by lysis of the medial layer of the arterial wall [5]. While histology remains the gold standard for diagnosis, the advancement of imaging techniques has led to greater use of clinical and imaging findings to establish the diagnosis. Given the consistent clinical history and characteristic imaging findings, biopsy was not pursued in our patient due to the associated risk.

The prognosis of SAM is not well-delineated, but the available literature suggests that it is typically a self-limiting disease, with progression demonstrated in ∼20% of patients, with either stability or regression observed in the remaining patients [4]. Management is determined by clinical presentation but can involve surgical, endovascular or medical intervention. There are no established guidelines on the medical management of SAM, although optimal control of blood pressure is considered the cornerstone of therapy to prevent propagation of dissection and further lysis of the arterial wall. There is no role for immunosuppression in the management of SAM. Therefore recognition of this syndrome may spare patients the risks associated with the inappropriate use of immunosuppressive therapies. Our patient was managed with anti-hypertensive medication as well as low-dose antiplatelet therapy. Interval 3 month imaging did not demonstrate any disease progression. This case illustrates an uncommon presentation of abdominal pain, where careful clinical evaluation in concurrence with imaging findings can establish the diagnosis.

Rheumatology key message

• SAM is a vasculitis mimic. Characteristic clinical and imaging findings are diagnostic without histologic confirmation.

Disclosure statement: The authors declare there are no conflicts of interest to report.

Funding: JJP is supported in part by a National Institutes of Health grant (K23 AR073927).

Data availability statement

Data are available upon reasonable request by any qualified researchers who engage in rigorous, independent scientific research, and will be provided following review and approval of a research proposal and Statistical Analysis Plan (SAP) and execution of a Data Sharing Agreement (DSA). All data relevant to the study are included in the article.