aplasia aplasia aplasia (/əˈpleɪʒə/ (listen); 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. -plasia and -trophy anaplasia (structural differentiation loss within a cell or group of cells). aplasia (organ or part of organ missing) desmoplasia (connective tissue growth) dysplasia (change in cell or tissue phenotype) hyperplasia (proliferation of cells) hypoplasia (congenital below-average number of cells, especially when inadequate) metaplasia (conversion in cell type) neoplasia (abnormal proliferation) prosoplasia (development of new cell function) abiotrophy (loss in vitality of organ or tissue) atrophy (reduced functionality of an organ, with decrease in the number or volume of cells) hypertrophy (increase in the volume of cells or tissues) hypotrophy (decrease in the volume of cells or tissues) dystrophy (any degenerative disorder resulting from improper or faulty nutrition) aplastic anemia is the failure of the body to produce blood cells. it may occur at any time, and has multiple causes. examples acquired pure red cell aplasia aplasia cutis congenita aplastic anemia germ cell aplasia, also known as sertoli cell-only syndrome radial aplasia thymic aplasia, which is found in digeorge syndrome and also occurs naturally as part of the gradual loss of function of the immune system later in life