Definition is a rhetorical mode that can be used in something smaller or shorter than a full paper. You can use extended definition for several paragraphs only in a paper of much greater length. You also can add to a paper a one-paragraph definition--like a brief encyclopedia definition.
Immunodeficiency: Therapies include thymus transplantation and adoptive transfer of mature T cells (ATMTC) for individuals with complete DiGeorge syndrome and appropriate prophylaxis measures and monitoring autoimmune complications for incomplete or partial DiGeorge syndrome.
DiGeorge Syndrome. DiGeorge syndrome, or congenital thymic hypoplasia, is a rare condition in which a missing portion of chromosome 22 causes a child to be born without a thymus or with one that is underdeveloped. If your child has this condition, she is vulnerable to infection.