Pathogenesis (Annunziato et al): Administration of killed vaccine (formalin-inactivated virus) produces antibody to hemagglutinin but not antibody to hemolysin (F); the latter is needed to prevent cell-to-cell spread of the measles virus. It also primes the immune system for a hypersensitivity-type reaction on re-exposure.
Clinical findings:
(1) The patient has a history of (a) vaccination with a killed measles vaccine or (b) vaccination with a killed measles vaccine followed shortly afterwards by a live measles vaccine.
(2) There is a prodrome with high fever, malaise, nausea, cough, headache and myalgia.
(3) A rash starts on the extremities then spreads cephalad. The rash is a mixture of maculopapular, petechial, urticarial and/or vesicular lesions.
(4) Koplik's spots are absent.
(5) The patient may develop photophobia, conjunctivitis, coryza and a sore throat.
(6) The extremities may be edematous.
(7) The patient may develop interstitial pulmonary infiltrates with or without pleural effusions and with or without mediastinal lymphadenopathy. The patient may develop pulmonary nodules that may persist for years and which may calcify.
(8) Some patients develop a hepatitis.
Laboratory findings:
(1) marked increase in serum anti-measles antibody titer (often from undetectable levels)
(2) negative viral cultures for measles
(3) variable eosinophilia
(4) variable abnormalities of liver function tests
(5) variable thrombocytopenia
(6) Measles virions may be detected around deep dermal blood vessels in a skin biopsy.
The patients are often seriously ill and may need to be hospitalized. The course is usually prolonged.
The diagnosis is often missed, especially if:
(1) The rash is absent.
(2) The patient did not receive killed measles vaccine.
(3) Anti-measles antibodies are not measured.
