JPGN Reports · 5 authors, 5 centres
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This case report describes segmental arterial mediolysis (SAM) presenting as a pancreatic mass in a 2-year-old boy with recurrent acute pancreatitis. SAM is a rare, noninflammatory vasculopathy of unknown etiology that compromises arterial wall integrity, leading to ischemia, hemorrhage, and dissection. Clinicians should consider SAM in the differential diagnosis of pancreatic masses in children after excluding other vasculopathies, as early recognition can be life-saving.
**Background:** Segmental arterial mediolysis (SAM) is a rare, noninflammatory, nonatherosclerotic vasculopathy of unknown etiology that affects medium-sized arteries. It compromises vessel wall integrity, predisposing to ischemia, hemorrhage, and dissection. Most cases have been reported in adults; only two pediatric cases have been described previously—one in a preterm infant and one intracranial presentation in a 14-year-old. This case adds to the sparse pediatric literature and is unique in that diagnosis was made during the early clinical phase.
**Methods:** The authors present a single case report of a 2-year-old male. Clinical presentation, laboratory data, imaging findings, surgical management, and histopathology are described. The patient initially presented with acute pancreatitis (lipase: 2754 U/L) and a 3-cm pancreatic head lesion on MRI. He was managed supportively and discharged with a diagnosis of acute pancreatitis with acute necrotic collection. Six months later, he was readmitted for recurrent acute pancreatitis (lipase: 242 U/L). Laboratory findings included elevated WBC (15.9 TH/cm²) with neutrophil predominance, platelets 120 k/µL, hemoglobin 10.7 g/dL, and elevated CRP (10 mg/dL). MRCP showed enlargement of the pancreatic lesion with portal vein compression and signs of portal hypertension including gastric varices and splenomegaly. The patient underwent explorative laparotomy with pancreatoduodenectomy, pancreaticojejunostomy, and en-bloc portal vein resection without reconstruction. Intraoperatively, an 8 cm poorly circumscribed pancreatic head mass with portal vein compression and collateralization was found.
**Key Results:** Histopathology revealed organizing hemorrhage surrounded by fibrosis and bland myofibroblastic proliferation with dense collagen. An abnormal artery with intimal hyperplasia was identified adjacent to the hemorrhage. Movat staining demonstrated segmental loss of the internal elastic lamina and tunica media, indicative of aneurysm formation. No malignancy or abnormal lymph nodes were found. Additional vascular imaging showed no other vascular involvement. The findings were most consistent with a ruptured aneurysm secondary to noninflammatory vasculopathy, i.e., SAM. Three subsequent CT angiograms over a 2-year period showed no recurrence.
**Clinical Implications:** SAM should be considered in the differential diagnosis of pancreatic masses in pediatric patients, particularly when recurrent pancreatitis and vascular abnormalities are present. Diagnosis requires a combination of clinical features, angiography findings, and histopathology, with histology as the gold standard. SAM has two histologic stages: an injurious phase with lytic degeneration of the tunica media, and a reparative phase with intimal hyperplasia leading to stenosis. Key differential diagnoses include fibromuscular dysplasia (which typically causes stenosis rather than aneurysms and affects middle-aged females), neurofibromatosis, and connective tissue disorders such as Marfan syndrome and Ehlers-Danlos syndrome. Management should be multidisciplinary and may involve surgical resection or arterial embolization depending on presentation. This case highlights that SAM can present in very young children and that early recognition and intervention can lead to favorable outcomes.