A 48-year-old woman with diffuse cutaneous systemic sclerosis presents with progressive dyspnea on exertion. Echocardiography shows an estimated right ventricular systolic pressure of 58 mmHg. Pulmonary function tests show a markedly reduced DLCO (42% predicted) with preserved FVC. The most likely underlying mechanism of her pulmonary hypertension in this context is:
- A Pulmonary arterial hypertension (PAH) from obliterative vasculopathy ✓
- B Cor pulmonale due to interstitial lung disease
- C Left heart failure from myocardial fibrosis
- D Pulmonary embolism from antiphospholipid antibodies
Correct answer: A. Pulmonary arterial hypertension (PAH) from obliterative vasculopathy
Explanation
In systemic sclerosis, an isolated markedly reduced DLCO (out of proportion to mild or absent FVC reduction) with an elevated RVSP is the classic pattern of scleroderma-associated pulmonary arterial hypertension (Group 1 PAH). This results from intimal proliferation and fibrosis of small pulmonary arterioles, distinct from the ILD pattern (which shows both reduced FVC and DLCO proportionally). Annual echocardiographic screening is recommended in SSc. Right heart catheterization confirms diagnosis. ERA and PDE-5 inhibitors form the basis of treatment.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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