A Critical Review of Atypical Measles Syndrome

Atypical measles syndrome (AMS) is a form of measles infectious disease which differs from classical measles by an older age distribution, often by a polymorphous skin involvement, by nodular pulmonary infiltrates, by hepatic abnormal functions and by eosinophilia. A brief review of the atypical measles syndrome is presented. In addition to the clinical aspects of the disease, including the differences with classical measles, the biologic features of the condition have been described. A series of queries relating the syndrome then be raised and, whenever possible responded to. Thus, it appears that the atypical measles syndrome is possibly not contagious. Immune complexes formation may be critical to the pathogenesis of this disease. This condition is not often severe and very rarely fatal. This syndrome may be exceptionally related with the live attenuated anti-measles vaccine. In spite of a common belief on the absence of immune waning, it is possible that humoral waning may play an important role in the atypical measles syndrome. The specific immune mechanisms in AMS, based on the macaque model, involve probably immune complexes formation. It is suggested in this review, that immunity waning, mainly humoral immunity, plays a common role in the pathogenesis of all forms of AMS.