severe combined immunodeficiency

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A usually fatal congenital disorder of the immune system in which the body is unable to produce enough B cells and T cells to resist infection.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a congenital disease affecting T cells that can result from a mutation in any one of several different genes; children with it are susceptible to infectious disease; if untreated it is lethal within the first year or two of life