PETECHIAE & PURPURA:
Indicates bleeding from capillaries: Normally capillary bleeding is controlled by capillary wall and platelets. Hence petechiae and purpura are seen in following conditions:
1: Weak Capillary Wall or loss of capillary support. steroids, old age, atrophic skin, collagen disorders,
2: Inflammation of the small vessel such as small vessel vasculitis etc. Viral infections, rickettsial infection & any bacteremia such as meningococcus can cause endothelial infection of capillaries confusing the picture with vasculitis.
3: Low platelet count (Thrombocytopenia)
4: Platelet dysfunctions (though platelet count is normal but they are non functional). Uraemia, antiplatelet Drugs, serotonin, few genetic causes such as Bernard Solier and Glanzmann etc.
WHAT TO DO ?
Check platelet count & bleeding time. If count is normal but bleeding time is high it means functional disorders of platelets.
Screen for infection, vasculitis or Cushing if & when clinically indicated.