ex·an·the·ma 
(ĕg′zăn-thēmə) also ex·an·them (ĭg-zănthəm)
(ĕg′zăn-thēmə) also ex·an·them (ĭg-zănthəm)n. pl. ex·an·them·a·ta (-thĕmə-tə) or ex·an·the·mas also ex·an·thems
1. A skin eruption accompanying certain infectious diseases.
2. A disease, such as measles or scarlet fever, accompanied by a skin eruption.
[Late Latin exanthēma, from Greek, eruption, from exanthein, to burst forth : ex-, ex- + anthein, to blossom (from anthos, flower).]
ex·an′the·matic (ĭg-zăn′thə-mătĭk), ex′an·thema·tous (ĕg′zăn-thĕmə-təs) adj.