SCID
Meaning of SCID: SCID is a group of rare inherited disorders in which T lymphocyte function is severely impaired, leaving the immune system unable to fight infection.
Definition of SCID
SCID, severe combined immunodeficiency, is a group of rare, inherited disorders in which the immune system develops with severely impaired T lymphocyte function. Because T lymphocytes normally help coordinate much of the immune response, their absence or dysfunction leaves the body unable to mount an effective defense against many infections.
Depending on the specific genetic cause, B lymphocytes and natural killer cells may also be absent or reduced, though in some forms of SCID, B lymphocytes are present in normal numbers but cannot function properly without the signals T lymphocytes normally provide. Several different gene mutations can produce this pattern of combined immune failure.
Infants with SCID typically develop serious, repeated infections from bacteria, viruses, and fungi within the first months of life, and the condition is generally considered a medical emergency, since it is usually fatal without intervention to restore immune function.
Also known as
Used in a sentence
Newborn screening identified low T lymphocyte levels consistent with SCID.
Good to know
Some genetic forms of SCID leave B lymphocyte numbers normal while T lymphocyte failure still prevents a functional immune response, so an apparently normal B cell count does not rule out the diagnosis.