Palpable purpura in Henoch-Schonlein

[fleshwound]

Does it blanch when pressed, like a hemangioma?

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[artsydoc]

It's my understanding that the blood is accumulated in the skin (it's extravasated) not the vessels so there's nowhere for it to go when it's pressed so it does not blanch, it just stays sitting there in the skin. Petechiae and ecchymose also don't blanch.

 

[Phloston]

It's my understanding that the blood is accumulated in the skin (it's extravasated) not the vessels so there's nowhere for it to go when it's pressed so it does not blanch, it just stays sitting there in the skin. Petechiae and ecchymose also don't blanch.

Yeah, that's right.

Petechiae, purpura and ecchymoses don't blanch because the blood has extravasated. Blanching means the blood is still in the vessels and applying pressure diverts it.