A 30-year-old woman with SLE presents with worsening dyspnea and a loud P2. Echo shows pulmonary artery systolic pressure of 62 mmHg. ANA, anti-dsDNA, and anti-U1-RNP antibodies are positive. What is the pathophysiologic mechanism of pulmonary hypertension in this setting?

• A Chronic thromboembolism due to antiphospholipid antibodies (Group 4 PH)
• B Hypoxia from lupus pleuritis causing pulmonary vasoconstriction (Group 3 PH)
• C Left heart diastolic dysfunction causing back-pressure (Group 2 PH)
• D Pulmonary arterial hypertension from endothelial dysfunction and vasoproliferation (Group 1 PH) ✓

Explanation

In SLE, pulmonary arterial hypertension (PAH) occurs due to immune-mediated endothelial injury leading to proliferative arteriopathy, classified as Group 1 PH (WHO classification). Anti-U1-RNP antibodies are particularly associated with PAH in connective tissue diseases. This is treated with PAH-specific therapies (endothelin receptor antagonists, PDE-5 inhibitors, prostacyclins) alongside immunosuppression. Antiphospholipid syndrome causes Group 4 PH (CTEPH) through recurrent thromboembolism.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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