Bleeding may result from abnormalities in
Collagen is a protein that is important in maintaining strong blood vessels in the body. When collagen is abnormal or abnormal substances in the blood get into vessel walls, the vessels weaken and bleeding can develop.
Fragile blood vessels cause bleeding under the skin, leading to tiny red, purple or brown spots on the skin (petechiae), red or purple blemishes or bruises (purpura), and bruising. Most disorders caused by fragile blood vessels do not cause serious blood loss. The genetic disorder hereditary hemorrhagic telangiectasia is an exception.
Abnormalities of collagen in the blood vessels may occur in scurvy (due to lack of vitamin C in the diet) and in Ehlers-Danlos syndrome and other rare hereditary connective tissue disorders, including Marfan syndrome, osteogenesis imperfecta, and pseudoxanthoma elasticum, leading to an increased risk of bleeding in these disorders.
Blood vessels can also be weakened by deposits of abnormal proteins in their walls as occurs in amyloidosis, cryoglobulinemia, and hypergammaglobulinemic purpura, or by inflammation as in autoimmune vasculitis. For example, bleeding may be a prominent feature of immunoglobulin A–associated vasculitis, an inflammation of small blood vessels that is common during childhood.