Page 74 - Color Atlas Of Pathophysiology (S Silbernagl Et Al, Thieme 2000)

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or synthetic vitamin K 3 ) fail to be absorbed platelet survival time due to immune com-
due to the lack of bile salts (→ p.168); plexes). The chronic form occurs as an autoim-
– generalized malabsorption (→ p.152ff.); mune disease. Drug allergy can produce TCP
– destruction by antibiotics of the intestinal through the action of drugs (e.g., quinine or
flora, which through its synthesizing vita- sulfonamides) as haptens (→ p. 52). Acquired
min K 2 contributes significantly to supply- thrombocytopathies occur in uremia and dys-
ing the body with this substance. proteinemia (platelet coating). They can also
The inhibition of the vitamin K effect by cou- be caused by such drugs as acetylsalicylic acid
marin derivatives (phenprocoumon, warfarin, via their inhibitory effect on cyclo-oxygenase,
acenocumarol) is used for oral prophylaxis of an effect that is used in thrombosis prophylaxis.
thrombosis (anticoagulant treatment). Congenital thrombocytic HDs are the auto-
Consumption coagulopathy (= disseminated somal-dominant and autosomal-recessive he-
intravascular coagulation; → D2) is a coagula- reditary thrombocytopenias (abnormal plate-
tion disorder caused by acute or chronic acti- let production) with the following functional
vation of thrombin with clot formation and disorders:
platelet activation that secondarily results in – Membrane defects such as 1) deficiency of
hyperfibrinolysis. It is caused by large platelet glycoprotein Ib (→ F1) that disturb
amounts of tissue thromboplastin entering adhesion (Bernard–Soulier syndrome); 2)
the bloodstream, for example, in amniotic deficiency of glycoprotein complex IIa/IIIb
fluid embolism, extensive brain injury, malig- (→ F2), which inhibits aggregation and ad-
Blood nant disease (e.g., leukemia), or sepsis (e.g., hesion (Glanzmann–Naegeli thrombasthe-
petechiae in meningococcal septicemia [Wa-
nia);
3 terhouse–Friedrichsen syndrome]). Vascular – Diverse defects of storage or secretion, for ex-
causes are seen, for example, in aortic aneu- ample, deficiency of cyclo-oxygenase and
rysm (→ p. 236ff.), or in vascular malforma- thromboxane synthetase, in which ADP re-
tions as well as in ABO blood group mis- lease is reduced (storage pool deficiency);
matches, and due to enzyme action with cer- (→ F3).
tain snake poisons. Among the forms of HD of vascular cause are
The two groups of hemorrhagic diathesis the different kinds of hereditary von Wille-
caused by platelet abnormalities are thrombo- brand’s (vW) disease, a defect of vascular en-
cytopenias and thrombocytopathies. Acquired dothelium in which the vW factor is reduced
thrombocytopenias (TCPs) are the most com- or defective (→ F4). This weakens platelet ad-
mon HD. TCP is due to diminished platelet for- hesion and secondarily leads to factor VIII defi-
mation (aplastic TCP, e.g., in bone marrow tu- ciency, because the vW factor acts as a kind of
mors, radiation damage, or cobalamine or fo- carrier for this factor (complex formation).
late deficiency), to increased platelet destruc- Finally, there are a number of functional disor-
tion (thrombocytoclastic TCP), or platelet se- ders and tissue changes in the vascular wall
questration in an enlarged spleen. Markedly and connective tisue that are either congenital
increased bleeding tendency occurs when the (purpura simplex; Osler–Weber–Rendu dis-
number of platelets falls below 20 × 10 /µL. ease; Schönlein–Henoch disease), or acquired
3
Idiopathic TCP (Werlhof’s disease) is relatively (scurvy in vitamin C deficiency; drug-medi-
frequent, its acute form developing one to ated immune reactions).
three weeks after a viral infection (shortened

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