A severe atypical presentation of measles may appear in persons who were immunized between 1963 and 1967 with killed measles virus vaccine and who were later exposed to the wild virus. After a prodrome of fever, headache, abdominal pain, and myalgias, a rash develops on the hands and feet and advances toward the head. The eruption may be vesicular, urticarial, maculopapular, or hemorrhagic and is most prominent along body creases. Pneumonia, pleural effusion, and hilar lymphadenopathy are common in atypical measles. All persons vaccinated after 1967 received the live attenuated measles vaccine, which is not associated with the atypical measles syndrome.
Complications occur more commonly in adults, malnourished children, and immunocompromised patients.
Measles virus may further suppress host immune responses, leading to reactivation of latent tuberculosis or superimposition of new bacterial pneumonia, particularly among malnourished children. CNS involvement may precede the rash but usually begins 4 to 7 days after the eruption appears. In rare instances, a subacute sclerosing panencephalitis occurs as a complication of measles in children who were initially infected when younger than 2 years, but it develops only after a latent period of several years. Other measles complications include thrombocytopenia with associated purpura or bleeding, myocarditis, pericarditis, hepatitis, and severe keratitis progressing to blindness. In an epidemic setting, observation of the characteristic rash, fever, coryza, and conjunctivitis is sufficient to establish the diagnosis.