Hereditary cystic medial necrosis of aorta, especially in ascending aorta, with resulting dissection; marked by long limbs in proportion to torso, lens subluxation, slender and elongated digits, scoliosis, slipped upper femoral epiphysis, joint laxity, hernias, and retinal detachment. Condition is autosomal dominant in 80% of cases and sporadic in 20% of cases; defect is on 15q21.