Libman-Sacks endocarditis

**Definition:** A form of nonbacterial thrombotic (verrucous) endocarditis seen in autoimmune disease, mainly SLE and secondary/primary antiphospholipid syndrome (APS).

**Pathophysiology:** - Immune complex deposition and antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, anti-β2-glycoprotein I) cause valvular endothelial injury and a hypercoagulable state. - Platelets and fibrin deposit on the damaged valve, with fibrinoid necrosis, inflammation, and later fibrosis and scarring. - Vegetations are sterile, so blood cultures are negative.

**Pathology (high-yield):** - Small (1–4 mm), warty, friable, **verrucous** vegetations. - They form on **both the upper and lower surfaces of the valve leaflets**, which is a classic distinguishing feature. They can also involve the undersurface, chordae, and mural endocardium. - The **mitral valve** is most commonly affected, then the aortic valve. - Histology shows fibrin, platelets, and inflammatory cells, with hematoxylin bodies in SLE.

**Clinical features:** - Often asymptomatic and found incidentally on echocardiography or at autopsy. - Valvular regurgitation (mitral or aortic) can develop, and stenosis is less common. - The main complication is **systemic embolization**, which can cause stroke or TIA, peripheral emboli, or renal infarcts. - It can serve as a nidus for superimposed infective endocarditis.

**Diagnosis:** - Echocardiography, with TEE more sensitive than TTE, shows irregular valve thickening and vegetations. - Negative blood cultures help distinguish it from infective endocarditis. - Check antiphospholipid antibodies, ANA, and anti-dsDNA.

**Treatment:** - Treat the underlying disease with glucocorticoids and immunosuppression for active SLE. - Anticoagulation (warfarin) is used for APS or embolic events. DOACs are generally avoided in APS, especially triple-positive APS. - Surgery is reserved for severe valvular dysfunction or recurrent emboli despite anticoagulation.

**Board comparison of vegetations:** - **Infective endocarditis:** large, friable vegetations. *S. aureus* affects normal valves and IV drug users (tricuspid), and viridans streptococci affect damaged valves. - **Nonbacterial thrombotic endocarditis (marantic):** small, bland vegetations along the **line of closure**. It is associated with malignancy (especially mucinous adenocarcinoma) and hypercoagulable states. - **Rheumatic heart disease:** small vegetations along the line of closure, with Aschoff bodies, "fish-mouth" mitral stenosis, and a history of group A strep. - **Libman-Sacks:** small to medium vegetations on **both sides** of the valve, associated with SLE.

**Mnemonic:** "SLE → Libman-Sacks → Sterile, on Several surfaces (both sides of the valve)." Another is "Libman-Sacks = Lupus = Look on both sides."

**Associated:** SLE, APS, possibly other autoimmune conditions. The vegetations are sterile and the cultures negative.