<unk>  (; from Greek a, "not", "no" + plasis, "formation") is a birth defect where an organ or tissue is wholly or largely absent. It is caused by a defect in a developmental process. Aplastic anemia is the failure of the body to produce blood cells. It may occur at any time, and has multiple causes. __TOC__
Aplasia
Agenesis
Atrophy
Metaplasia
Hypoplasia
Variegation 
Hyperplasia
Dysplasia