A 3-year-old boy with suspected systemic-onset JRA develops tachycardia and dyspnea on the fifth day of hospitalization. He complains that his chest hurts. Auscultation of the heart reveals a “friction rub” sound. The most likely diagnosis is:
A. Heart failure.
B. Pneumonia.
C. Asthma.
D. Pericarditis.
E. Mitral valve prolapse.