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.
Zellweger syndrome is a rare, inherited metabolic disorder that affects peroxisomes, organelles found in almost all body cells. Peroxisomes are responsible for many important cell processes, including energy metabolism, which means that Zellweger syndrome can severely impact the body.