Platelet function disorders
All are rare and autosomal recessive. They are due to the following:
· Defective platelet membrane specific glycoproteins, which cause defective adhesion to fibrinogen, e.g. Glanzmann disease (thromboasthenia), Bernard-Soulier syndrome (BSS), vWD (usually AD).
· Defective or deficient platelet granules (normal release induces coagulation cascade, vasoconstriction, platelet aggregation), e.g. TAR syndrome, Chediak–Higashi syndrome.
May be s to drugs, e.g. NSAIDs, corticosteroids, antihistamines, renal disease, liver disease, and diets rich in garlic, ginger, and Indian spices.
· Easy bruising and purpura.
· Mucocutaneous bleeding.
· Positive family history is common (although in most AR syndromes both parents are unaffected).
· Usually normal platelet count (except in BSS which usually has mild thrombocytopenia).
· i Platelet size, e.g. giant platelets in BSS.
· Prolonged PFA.
· If congenital platelet functional disorder suspected, perform PFA followed by formal platelet aggregation studies using ristocetin, collagen, adenosine 5-diphosphate (ADP), arachidonic acid, and adrenaline; and platelet nucelotide ratios. Interpretation is complex, so seek haematologist help.
· Control bleeding, e.g. apply pressure in mild cases.
· Correct underlying abnormality or stop responsible drug.
· Give tranexamic acid for minor bleeding, e.g. mouth washes or systemically 20–25mg/kg tds for < 5 days.
· Give platelet transfusion if bleeding severe or to cover for surgery. Note: Need to give HLA matched platelets to avoid HLA specific anti-platelet antibody formation, if child likely to need frequent transfusions.
· Avoid drugs that inhibit platelet function, e.g. NSAIDs and IM injections.
· Consider oral contraceptives in teenage girls to control menorrhagia.
Prognosis is generally good with normal life expectancy. Serious bleeding is rare, but can be difficult to manage, particularly in children with multiple anti-platelet or anti-HLA antibodies.