Diagnostic Pitfall: Mixed Connective Tissue Disease‐Associated Pulmonary Hypertension Presenting With Postpartum Right‐Sided Heart Failure in a 21‐Year‐Old—Case Report

Mixed connective tissue disease is a multisystem autoimmune condition characterized by overlapping clinical and serological features related to anti‐U1‐RNP antibodies of at least two connective tissue diseases. It may present with myocarditis, pericarditis, pulmonary arterial hypertension, and, less commonly, heart failure. We present a 21‐year‐old female with bilateral foot swelling, cough, and shortness of breath 3 months after a vaginal delivery. On examination, she was hypotensive (90/70 mmHg), with an elevated jugular venous pressure, a pulmonary systolic murmur with loud P2, and a tricuspid regurgitation murmur. Bronchial breath sounds and fine crepitations were present in both lower lung fields. She was evaluated initially for suspected postpartum cardiomyopathy. Transthoracic echocardiography was suggestive of a probable moderate to severe PAH. High‐resolution computed tomography showed bilateral moderate pleural effusions, honeycombing with partial atelectasis of the underlying lung, and cardiomegaly. Computed Tomography Pulmonary Angiography (CTPA) showed findings likely consistent with probable mild pulmonary hypertension. An antinuclear antibody panel was performed and was positive for anti‐U1‐RNP, SS‐A, SS‐B, and Jo‐1 antibodies. She was started on Lasix 40 mg, Aldactone 25 mg, lisinopril 10 mg, and heparin. Treatment with 20 mg of prednisolone was started and gradually tapered. Her anasarca and dyspnea improved, and she was discharged with follow‐up arranged with cardiology and rheumatology. Timely identification of MCTD‐associated pulmonary hypertension and its cardiovascular complications is essential and allows early commencement of treatment, which further prevents the patients from developing heart failure.