Bleeding disorders. Defects in clotting
Blood-clotting defects have different clinical manifestations.
The most characteristic featureof such defects, as typified
by hemophilia, are recurrent, crippling hemorrhages
into joints and muscles and bleeding into body cavities.
The diagnosis of hemostatic defects depends on clinical
and laboratory data. Investigation ofthe affected person's
family history is important because many of these conditions
are inherited. The personal history reveals the type
of bleeding and the possible effects of drugs, chemicals,
allergy, infection, or dietary abnormalities. Examination
reveals visible hemorrhages or vascular lesions and
the effects of internal bleeding. Platelets are evaluated
by counting them, examining their appearance, and testing
functions such as the bleeding time, platelet adhesiveness,
and platelet aggregation. Tests of clotting function
include such indicators as the prothrombin time and
the partial thromboplastin time. These tests allow a
deficiency of any of the clotting factors to be identified
and a quantitative assessment of activity of individual
factors to be made. Most cases of abnormal bleeding
can thus be traced to specific defects (see table).
Precise diagnosis often permits specific and effective
treatment.
