Amyloid purpura is a condition marked by bleeding under the skin (purpura) in some individuals with amyloidosis.[1] Its cause is unknown, but coagulation defects caused by amyloid are thought to contribute.
The precise cause of amyloid purpura is unknown, but several mechanisms are thought to contribute.[2] One may be a decrease in the level of circulating factor X,[2]aclotting factor necessary for coagulation. The proposed mechanism for this decrease in factor X is that circulating amyloid fibrils bind and inactivate factor X.[2] Another contributing factor may be enhanced fibrinolysis,[2] the breakdown of clots. Subendothelial deposits of amyloid may weaken blood vessels and lead to the extravasation of blood.[2][3] Amyloid deposits in the gastrointestinal tract and liver may also play a role in the development of amyloid purpura.[2]
Amyloid purpura affects a minority of individuals with amyloidosis.[1] For example, purpura is present early in the disease in approximately 15% of patients with primary systemic amyloidosis.[4]
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