The Collaborative International Dictionary of English v.0.48:

Exanthema \Ex`an*the"ma\, n.; pl. Exanthemata. [L., fr. Gr.?,
   fr.? to burst forth as flowers, break out, as ulcers; ?, ?,
   out + 'anqei^n to bloom, 'a`nqos flower: cf. F.
   exanth[`e]me.] (Med.)
   An efflorescence or discoloration of the skin; an eruption or
   breaking out, as in measles, smallpox, scarlatina, and the
   like diseases; -- sometimes limited to eruptions attended
   with fever. --Dunglison. Exanthematic

WordNet (r) 3.0 (2006):

exanthema
    n 1: eruption on the skin occurring as a symptom of a disease
         [syn: exanthem, exanthema, skin eruption]