We firstly report on a dystrophic preterm infant with segmental arterial mediolysis (SAM) found in arteries of placental, umbilical and cerebral tissues. These arterial lesions of unknown etiology developing in the elderly are characterized by segmental lysis of the abdominal splanchnic arteries followed by aneurysms and acute bleeding. Typically, the lesions occur in a skip pattern. We could find a small number of SAM in the spleen but much more in placental and umbilical tissues. Rarely, a vascular elastosis and splitting of individual vessels in the spleen and lung could be detected. The histological findings are similar to that of adult patients.