Marfan syndrome can affect many body systems and the symptoms of the disease vary greatly. Features may include: i) Tall and slender build, ii) disproportionately long arms, legs, fingers and toes iii) breastbone that protrudes outward or dips inward iv) high, arched palate and crowded teeth v) heart murmurs vi) extreme nearsightedness vii) Curved spine viii) Flat feet. Aortic aneurysm; Aortic dissection and Valve malformations are the commonest complications to be anticipated in his condition. Diagnostic tests include: Echocardiogram; for the functional aspect of the heart. Slit-lamp exam: for lens dislocation, cataracts or a detached retina. In your son?s case is it being diagnosed by the doctor? Simple stretch marks is not a way to presume Marfan's syndrome though they are part of it. If your doctor diagnoses about the problem you can browse for Marfan's over the Internet.