Idiopathic thrombocytopenia is a diagnosis of exclusion.
Two distinct forms are recognised:
- an acute, transient disorder, mainly of children. The acute form is defined as lasting less than six months.
- a chronic, insidious form, mainly of adults, lasting more than six months
The pathogenesis of the two forms is thought to be different. The acute form is due to immune complexes; the chronic form, to specific IgG antiplatelet antibodies.