Case Report: Nutcracker Syndrome Triggered by Rapid Weight Loss in a Patient With Systemic Lupus Erythematosus.

Nutcracker syndrome (NCS) is a rare vascular disorder characterized by compression of the left renal vein, typically causing hematuria, proteinuria, and flank pain. Although NCS is often linked with weight loss and anatomical variations, no previous reports have connected it to systemic lupus erythematosus (SLE). We describe a 44-year-old male with SLE who developed NCS after rapid weight loss, presenting with abdominal pain, hematuria, and proteinuria. Imaging confirmed left renal vein compression between the aorta and the superior mesenteric artery. This finding suggests that significant weight reduction in SLE may trigger NCS by altering retroperitoneal fat and vascular structures. A literature review reveals a consistent association between NCS and marked weight loss, as well as possible coexistence with other vascular compression syndromes, such as superior mesenteric artery syndrome. Clinicians should consider NCS in SLE patients with sudden weight changes to ensure timely diagnosis and prevent complications.