Vascular disorders are characteristically manifest by petechiae, purpura, or telangiectasia. Although most vascular disorders are not strictly hematological diseases, many are characterized by or accompanied by a significant hemorrhagic diathesis and often present in this manner. The diagnosis for most vascular disorders commonly requires an autoimmune investigation or connective tissue biopsy. The simplest classification of vascular disorders is into hereditary and acquired, with acquired types being more common. The Ehler-Danlos syndrome (ED syndrome) is a rare connective tissue disorder that is inherited by autosomal dominance. The basic pathology of ED syndrome is poorly understood, but appears to represent a decrease in collagen and an increase in elastic tissue. Osteogenesis imperfecta is one of the more common hereditary collagen vascular diseases and is inherited as an autosomal dominant trait. Pseudoxanthoma elasticum, unlike the other hereditary collagen vascular diseases, often does not become manifest until the second or third decade in life.