Diagnosis in the other patients was based on clinical presentation and timing relative to LAV vaccination; it was also confirmed by PCR in P8 (PCR on throat swab positive for measles, mumps, and rubella and PCR on cerebrospinal fluid positive for mumps), P11 (PCR on throat swab positive for mumps and rubella), and P15 (PCR on urine positive for mumps and IgM against mumps virus detected in serological tests). The gene discussed is CD40LG; the disease is measles.