The Haemorrhagic Diathesis.

The primary purpuras form a single clinical entity.Variations in the number of platelets can occur without the production of haemorrhages. These variations are the result of the condition of the capillaries and are not the cause of haemorrhages. The platelets may vary in any form of purpura, primary or secondary.The essential cause of the haemorrhagic state is a defect or increased permeability of the capillary endothelium.Purpura is allied to urticaria, the Henoch-Schönlein type being an intermediate state.