A 6-year-old girl that looks tall and thin with light skin. On examination she has a peculiar malar flush

(C). In Homocystinuria, thromboembolic episodes involving both large and small vessels, especially those of the brain, are common and may occur at any age. Optic atrophy, paralysis, cor pulmonale, and severe hypertension (from renal infarcts) are among the serious consequences of thromboembolism, which is caused by changes in the vascular walls and increased platelet adhesiveness secondary to elevated homocystine levels