Boston exanthema [Boston; Gk, ex, out, anthema, blossoming] , an epidemic disease characterized by scattered, pale red maculopapules on the face, chest, and back, occasionally accompanied by small ulcerations on the tonsils and soft palate. There is little or no adenopathy, and the rash disappears spontaneously in 2 or 3 weeks. It is caused by echovirus 16 and requires no treatment. Compare herpangina.