Purpura

81–3

Key history Include family history, drug history and features of the purpura such as post trauma or spontaneous, recurrent episodes of bleeding and whether any bleeding is out of proportion to the trauma.

Diagnostic tips

• Platelet abnormalities present as early bleeding following trauma.

• Coagulation factor deficiencies present with delayed bleeding after initial haemostasis is achieved by normal platelets.

• A normal response to previous coagulation stresses (e.g. dental extraction, circumcision or pregnancy) indicates an acquired problem.

DxT

• Bruising + oral bleeding + epistaxis → ITP

• Menorrhagia + bruising + increased bleeding (incisions, dental, mouth) → vWD

• Spontaneous haemarthrosis + muscle bleeds + delayed bleeding → haemophilia A

• Arthalgia + purpuric rash ± abdominal pain → H–SP

Reference platelet counts

• Normal: 150–400 × 10⁹/L

• Purpura threshold: <50 × 10⁹/L