Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 38-year-old woman is evaluated for a 6-month history of progressive fatigue and dyspnea on exertion. Over the past 2 years she has noted episodes of hand swelling, joint pain, blue color change of her fingers with cold exposure, and difficulty swallowing. She takes no medications.

On physical examination, temperature is 36.9 °C (98.4 °F), blood pressure is 126/84 mm Hg, pulse rate is 88/min, and respiration rate is 18/min. Cardiac examination reveals an accentuated pulmonic component of S₂ and a grade 2/6 holosystolic murmur. Muscle strength is normal.

Laboratory studies reveal a serum creatine kinase level of 312 units/L, an antinuclear antibody titer of 1:1280 (speckled pattern), and high positive anti-U1-ribonucleoprotein antibodies.

Pulmonary function tests show a DLCO of 55% of predicted with normal FEV₁ and lung volumes. Chest radiograph is normal. Electrocardiogram reveals right axis deviation. Echocardiogram shows 2+ tricuspid regurgitation, an enlarged right atrium, normal left and right ventricular function, and an estimated systolic pulmonary artery pressure of 40 mm Hg. High-resolution CT of the chest is normal. Ventilation/perfusion scan results are normal.

Which of the following is the most appropriate next step in management?

A. Muscle biopsy
B. Radionuclide stress test
C. Repeat echocardiography and pulmonary function tests in 1 year
D. Right heart catheterization

MKSAP Answer and Critique

The correct answer is D. Right heart catheterization. This item is available to MKSAP 16 subscribers as item 26 in the Rheumatology section.

Right heart catheterization is appropriate for this patient to evaluate for pulmonary arterial hypertension (PAH). She has symptoms and signs suggestive of an underlying diagnosis of mixed connective tissue disease (MCTD), which is characterized by overlapping clinical features of systemic lupus erythematosus, polymyositis, and systemic sclerosis, with high titers of antinuclear and anti-U1-ribonucleoprotein (RNP) antibodies. PAH may also occur, which is the most common disease-related cause of death in patients with MCTD.

This patient has Raynaud phenomenon, hand swelling, joint pain, dysphagia, high-titer speckled antinuclear antibodies, and high-titer RNP antibodies, all of which are typical findings of MCTD. This patient’s symptoms of dyspnea on exertion, isolated low DLCO, and elevated estimated systolic pulmonary artery pressure on echocardiogram all suggest PAH. Therefore, right heart catheterization is indicated.

Despite the patient’s mildly elevated serum creatine kinase level, muscle biopsy is not necessary, because her muscle strength is normal. Patients with MCTD may have subclinical myositis, but respiratory muscle weakness causing dyspnea would be a late finding associated with more profound myositis.

Radionuclide stress test is not indicated for this patient, whose abnormal DLCO and systolic pulmonary artery pressure on echocardiogram are not suggestive of ischemic cardiac disease as the cause for her dyspnea.

In patients with confirmed MCTD without cardiopulmonary symptoms and with normal baseline pulmonary function testing and echocardiogram, yearly repeat tests are appropriate for routine monitoring. It is an inappropriate choice for this symptomatic patient with findings highly suggestive of PAH.

Key Point

• Pulmonary arterial hypertension is the most common disease-related cause of death in patients with mixed connective tissue disease.

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