BLEEDING DISORDERS CAUSED BY VESSEL WALL ABNORMALITIES

Disorders within this category, sometimes called nonthrombocytopenic purpuras, are relatively common but do not usually cause serious bleeding problems. Most often, they induce small

hemorrhages (petechiae and purpura) in the skin or mucous membranes, particularly the gingivae. On occasion, however, more significant hemorrhages can occur into joints, muscles, and

subperiosteal locations or take the form of menorrhagia, nosebleeds, gastrointestinal bleeding, or hematuria. The platelet count, bleeding time, and results of the coagulation tests (PT, PTT)

are usually normal.

The varied clinical conditions in which hemorrhages can be related to abnormalities in the vessel wall include the following:

• Many infections induce petechial and purpuric hemorrhages, but especially implicated are meningococcemia, other forms of septicemia, infective endocarditis, and several of the

rickettsioses. The involved mechanism is presumably microbial damage to the microvasculature (vasculitis) or disseminated intravascular coagulation (DIC). Failure to recognize

meningococcemia as a cause of petechiae and purpura can be catastrophic for the patient.

• Drug reactions sometimes induce cutaneous petechiae and purpura without causing thrombocytopenia. In many instances, the vascular injury is mediated by drug-induced

antibodies and deposition of immune complexes in the vessel walls, leading to hypersensitivity (leukocytoclastic) vasculitis ( Chapter 11 ).

• Scurvy and the Ehlers-Danlos syndrome are associated with microvascular bleeding resulting from impaired formation of collagens needed for support of vessel walls. The same

mechanism may account for spontaneous purpura commonly seen in the very elderly. The predisposition to skin hemorrhages in Cushing syndrome, in which the protein-wasting

effects of excessive corticosteroid production cause loss of perivascular supporting tissue, has a similar etiology.

• Henoch-Schönlein purpura is a systemic hypersensitivity disease of unknown cause characterized by a purpuric rash, colicky abdominal pain (presumably due to focal

hemorrhages into the gastrointestinal tract), polyarthralgia, and acute glomerulonephritis ( Chapter 20 ). All these changes result from the deposition of circulating immune

complexes within vessels throughout the body and within the glomerular mesangial regions.

• Hereditary hemorrhagic telangiectasia is an autosomal dominant disorder characterized by dilated, tortuous blood vessels with thin walls that bleed readily. Bleeding can occur

anywhere in the body but is most common under the mucous membranes of the nose (epistaxis), tongue, mouth, and eyes and throughout the gastrointestinal tract.

• Amyloid infiltration of blood vessels. Systemic amyloidosis is associated with perivascular deposition of amyloid and consequent weakening of blood vessel wall. This is most

commonly observed in plasma cell dyscrasias ( Chapter 14 ) and is manifested as mucocutaneous petechiae.

Bleeding in these conditions is rarely life threatening with the exception of some cases of hereditary telangiectasia. Recognition of the presenting symptoms should prompt further studies

to establish a specific diagnosis.

Date: 2016-04-22; view: 794