[Three cases of suspected re-infection of mumps virus].

A 32-year-old woman, 5-year-old girl, and 33-year-old man visited our otorhinolaryngology outpatient clinic with tumentia of the unilateral parotid gland. A high titer of serum IgG antibodies against the mumps virus was detected. Around the same time, other members of their families had the same parotid tumentia, and they were diagnosed as having their first mumps infection. Therefore, the diagnosis of the three cases was strongly suspected to be re-infection with mumps. In Japan, it was classically believed that the mumps virus infection occurs only once in patients and reinfection doesn't occur. However, some pediatricians in Japan have reported that re-infection with mumps is strongly suspected when high titers of serum IgG antibodies against the mumps virus are found at the initial visit. It is now believed many more examples of mumps re-infection cases have existed than we previously believed. When high titers of serum IgG antibodies against the mumps virus are detected at an initial visit in patients who have had mumps previously, re-infection should be strongly suspected. And to make it certain, we suggest that the mumps IgG antibodies should be checked twice to confirm the diagnosis. If elevation of the IgG antibodies persist, the diagnosis will be much more certain.