di·ath·e·sis 
(dī-ăthĭ-sĭs)
(dī-ăthĭ-sĭs)n. pl. di·ath·e·ses (-sēz′)
1. A hereditary predisposition of the body to a disease, a group of diseases, an allergy, or another disorder.
2. Grammar See voice.
[Greek, disposition, condition, from diatithenai, diathe-, to dispose : dia-, dia- + tithenai, to place, set; see dhē- in the Appendix of Indo-European roots.]
di′a·thetic (dī′ə-thĕtĭk) adj.