Case Report: A rare coexistence with severe aortic root dilatation and nutcracker phenomenon in pediatric Marfan syndrome.

Marfan syndrome (MFS) is a multisystem connective tissue disorder affecting the cardiovascular, ocular, and skeletal systems. We report a case of a 13.5-year-old boy who presented with excessive linear growth. Diagnostic evaluations revealed severe aortic root dilatation, repeatedly positive occult blood in urine, and ultrasonographic findings suggestive of left renal vein entrapment. Genetic testing identified a pathogenic variant in the FBN1 gene. The patient was ultimately diagnosed with Marfan syndrome complicated by left renal vein entrapment syndrome (nutcracker phenomenon). The co-occurrence of severe aortic root dilatation and left renal vein entrapment syndrome in childhood Marfan syndrome is relatively uncommon. This case may provide valuable insights for clinical diagnosis and management.