- Anti-phospholipid anti-body syndrome; may have hx fetal loss during first trimester pregnanacy
- Endothelial damage from trauma, surgery, xrt, cocaine
- Hyperhomocystinemia
- Pregnancy - w/hypercoag state extending ~6w post partum
- Often idiopathic or assumed related to traditional RFs of: HTN, hyperlipidemia, smoking, early family hx, diabetes