Measles encephalomyelitis in a patient with a history of vaccination.

Secondary vaccine failure (SVF) of measles is generally believed to run a milder course of illness than an ordinary course of infection. Severe complications such as central nervous system involvement have rarely been reported. A 12 year old girl, who had received a live attenuated measles vaccine 10 years earlier, developed an encephalomyelitis in the absence of symptoms indicative of ordinary measles such as Koplik spots. Anti-measles hemagglutination inhibition (HI) titer and measles IgM and IgG antibody titers were measured in a commercial laboratory. Measles virus genomic sequence was detected by polymerase chain reaction. Both serum and cerebrospinal fluid (CSF) samples obtained at acute phase already showed extremely high titers of HI (x8192 in serum and x1024 in CSF, respectively) and IgG antibody along with the presence of IgM antibody. Polymerase chain reaction detected the measles virus genomic sequence in the acute phase CSF. The patient's definite history of measles vaccination, high titers of HI and IgG antibodies observed at the very early stage of illness and the clinical course indicated that this patient has an encephalomyelitis due to SVF of measles. It is suggested that measles virus can be a pathogen of encephalitis without symptoms indicative of ordinary measles in individuals who received live attenuated measles vaccines.