Pulmonary veno-occlusive disease as a primary cause of pulmonary hypertension in a patient with mixed connective tissue disease

Mixed connective tissue disease (MCTD) is a systemic disease seen in a group of patients with overlapping clinical features of lupus, scleroderma, polymyositis, and rheumatoid arthritis. A defining feature of MCTD is the presence of antibodies against the U1-ribonucleoprotein (U1-RNP) complex. Pulmonary hypertension is the major cause of death in MCTD. We report an autopsy case of MCTD with pulmonary hypertension. The U1-RNP antibody of this patient was 171.9 U (normal < 25.0 U). The immediate cause of death was attributed to acute pulmonary embolism at left lower lobe. A severe vasculopathy characterized by fibrotic occlusion of small veins and venules, associated with prominent capillary congestion, was consistent with pulmonary veno-occlusive disease (PVOD). This is the first case reported in which PVOD is the primary cause of pulmonary hypertension in MCTD.