Encyclopedia of Health and Medicine

294 The Immune System and Allergies
disorder far more common than doctors have long
believed. Early diagnosis and treatment can minimize
the consequences of the inflammation and
fibrosis and allow improved QUALITY OF LIFE.
See also AUTOIMMUNE DISORDERS; EYE; GRANULOMA;
IMMUNE DISORDERS; LIVING WITH IMMUNE DISORDERS;
LYMPH NODE; OFF-LABEL USE; SCAR.
seasonal allergies
See ALLERGIC RHINITIS.
severe combined immunodeficiency (SCID) A
rare, genetic immune disorder in which an infant
is born with severely deficient immune capability
due to the absence of leukocytes. Because the
infant receives PASSIVE IMMUNITY from his or her
mother at birth (and through BREASTFEEDING), the
deficiency often is not apparent until age three to
six months or when the infant begins to receive
routine immunizations. Doctors may suspect SCID
if there are other family members who have
IMMUNODEFICIENCY disorders. Most often the
infant’s immune status becomes suspect when
there are recurrent or severe infections that a
healthy IMMUNE RESPONSE would accommodate.
Some babies develop deep abscesses, such as in
the LIVER. Others have chronic OTITIS media (middle
EAR INFECTION) or SINUSITIS (sinus infection).
Early diagnosis and treatment are essential.
When doctors suspect and test for SCID within the
infant’s first three months of life, a BONE MARROW
TRANSPLANTATION can provide the ability to produce
lymphocytes, essentially curing the immunodeficiency.
Most often, however, parents and doctors
do not suspect an immune problem until the child
is six months to a year old. By that time other features
of the IMMUNE SYSTEM have developed
enough to reject a BONE MARROW transplant unless
IMMUNOABLATION first destroys the child’s own bone
marrow.
Bone marrow transplantation after age six
months requires extended IMMUNOSUPPRESSIVE
THERAPY to allow the new BLOOD STEM CELLS to take
root and become self cells within the body. The
child may also need ANTIBIOTIC PROPHYLAXIS and
GAMMAGLOBULIN injections to bolster the immune
response until the transplant fully takes hold.
Without treatment SCID is fatal by two years of
age and often in the first year of life. With bone
marrow transplantation the child has a good
chance for normal development and a relatively
healthy life.
See also ABSCESS; COMMON VARIABLE IMMUNE DEFI-
CIENCY (CVID); GENETIC DISORDERS; INHERITANCE PAT-
TERN; LEUKOCYTE; LIVING WITH IMMUNE DISORDERS;
LYMPHOCYTE; PARTIAL COMBINED IMMUNODEFICIENCY
(PCID).
Sjögren’s syndrome An autoimmune disorder
that affects the glands that provide moisture for
the mucous membranes, notably the lacrimal
(tear) glands and the SALIVARY GLANDS. Sjögren’s
syndrome exists in one of three forms:
• primary, in which the only structures it affects
are the exocrine glands and the main symptom
is dryness
• secondary, in which Sjögren’s syndrome
appears in conjunction with another autoimmune
disorder, typically RHEUMATOID ARTHRITIS,
scleroderma, or SYSTEMIC LUPUS ERYTHEMATOSUS
(SLE)
• ocular, in which symptoms affect only the eyes
(lacrimal glands)
Symptoms and Diagnostic Path
Symptoms depend to some extent on the affected
glands, which nearly always include the salivary
glands and the lacrimal glands. The lack of moisture
to the eyes can cause corneal ABRASIONS and
PHOTOSENSITIVITY. However, symptoms may involve
glands in mucous tissues throughout the body.
Dryness affecting other mucous membranes may
result in
• frequent nosebleeds (INFLAMMATION of the nasal
passages)
• PERICARDITIS (inflammation of the membrane
sac surrounding the HEART)
• BRONCHITIS (inflammation of the airways in the
LUNGS)
• VAGINITIS (inflammation of the VAGINA)
There are no specific tests to diagnose Sjögren’s
syndrome. A Schirmer’s test determines the moisture
content of the eyes; salivary gland biopsy can
reveal fibrosis and granulation typical of the
inflammatory process. Doctors generally consider