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http://www.nhlbi.nih.gov/health/dci/Diseases/sarc/sar_whatis.html
What is sarcoidosis?
Sarcoidosis is a systemic granulomatous disease of unknown
etiology that primarily affects the lung, although multi-organ
involvement frequently occurs.
Sarcoidosis (sar"koi-do'sis)
involves inflammation that produces tiny lumps of cells in
various organs in your body. The lumps are called granulomas (gran"u-lo'mahs)
because they look like grains of sugar or sand. They are very
small and can be seen only with a microscope.
These tiny
granulomas can grow and clump together, making many large and
small groups of lumps. If many granulomas form in an organ,
they can affect how the organ works. This can cause symptoms
of sarcoidosis.
Sarcoidosis can
occur in almost any part of your body, although it usually
affects some organs more than others. It usually starts in one
of two places:
- Lungs
- Lymph nodes, especially the lymph nodes in your chest
cavity.
Sarcoidosis also
often affects your:
Less often,
sarcoidosis affects your:
- Spleen
- Brain
- Nerves
- Heart
- Tear glands
- Salivary glands
- Bones and joints.
Rarely,
sarcoidosis affects other organs, including your:
- Thyroid gland
- Breasts
- Kidneys
- Reproductive organs.
Sarcoidosis almost
always occurs in more than one organ at a time.
Sarcoidosis has an
active and a nonactive phase:
- In the active phase, the
granulomas form and grow. In this phase, symptoms can
develop, and scar tissue can form in the organs where the
granulomas occur.
- In the nonactive phase, the inflammation goes down, and
the granulomas stay the same size or shrink. But the scars
may remain and cause symptoms.
The course of the
disease varies greatly among people.
- In many people, sarcoidosis
is mild. The inflammation that causes the granulomas may get
better on its own. The granulomas may stop growing or
shrink. Symptoms may go away within a few years.
- In some people, the inflammation remains but doesn't get
worse. You may also have symptoms or flare-ups and need
treatment every now and then.
- In other people, sarcoidosis slowly gets worse over the
years and can cause permanent organ damage. Although
treatment can help, sarcoidosis may leave scar tissue in the
lungs, skin, eyes, or other organs. The scar tissue can
affect how the organs work. Treatment usually does not
affect scar tissue.
Changes in
sarcoidosis usually occur slowly (e.g., over months).
Sarcoidosis does not usually cause sudden illness. However,
some symptoms may occur suddenly. They include:
- Disturbed heart rhythms
- Arthritis in the ankles
- Eye symptoms.
In some serious
cases in which vital organs are affected, sarcoidosis can
result in death.
Sarcoidosis is not
a form of cancer.
There is no known
way to prevent sarcoidosis.
Sarcoidosis was
once thought to be an uncommon condition. It's now known to
affect tens of thousands of people throughout the United
States. Because many people who have sarcoidosis have no
symptoms, it's hard to know how many people have the
condition.
Sarcoidosis was
identified in the late 1860s. Since then, scientists have
developed better tests to diagnose it and made advances in
treating it.
What is inflammation?
Autoimmunity and sarcoidosis
Signs and symptoms of sarcoidosis
Causes of sarcoidosis
What Causes
Sarcoidosis?
The cause of sarcoidosis is not known. And,
there may be more than one thing that causes it.
Scientists think that sarcoidosis develops
when your immune system responds to something in the
environment (e.g., bacteria, viruses, dust, chemicals) or
perhaps to your own body tissue (autoimmunity).
Normally, your
immune system defends your body against things that it
sees as foreign and harmful. It does this by sending special
cells to the organs that are being affected by these things.
These cells release chemicals that produce inflammation around
the foreign substance or substances to isolate and destroy
them.
In sarcoidosis, this inflammation remains and
leads to the development of granulomas or lumps.
Scientists have not yet identified the
specific substance or substances that trigger the immune
system response in the first place. They also think that
sarcoidosis develops only if you have inherited a certain
combination of genes.
You can't catch sarcoidosis from someone who
has it.
More research is needed to discover what
causes sarcoidosis
The etiology remains unclear; however, environmental,
genetic, ethnic, and familial factors probably modify expression
of the disease. As an example, African Americans are at greater
risk of mortality and morbidity than are white Americans, and
more often have a family history of sarcoidosis.
Sarcoidosis, first described 125
years ago, It is likely that expression of
the disorder in response to one or more inciting agents is
modified by the genetics of the host immune response.
In addition, an infectious component
has long been suspected. Although many clinical features and
associated syndromes have been described, the phenotype of
sarcoidosis at diagnosis provides only limited information
about the etiology or pathogenesis of the disorder.
Getting a diagnosis
Treatment
Most patients with sarcoidosis
recover spontaneously, but some develop chronic, debilitating
disease. Corticosteroids and other drugs,
although effective at controlling disease activity, may not
influence the overall course of disease.
Immunomodulatory Therapy
Biologic Response Modifiers
Treatment duration
Prognosis
Spontaneous remission or disease stabilization is reported to
occur in approximately two-thirds of cases, but many patients
have chronic progressive disease.
-
About 4–7% of patients have
serious extrapulmonary (i.e., heart, central nervous, liver,
or eye) involvement at the time of presentation; this
possibility increases as the disease progresses.
-
Data on persistent disease and
relapses from centers in the United States that treat a large
number of patients with sarcoidosis vary from 20% in Iowa (4)
to more than 50% among patients in Philadelphia whose
treatment was stopped.
-
Mortality rates at referral
centers are high at 3–10%, whereas low mortality is
reported from nonreferral centers.
-
No good test for predicting
disease progression exists and better means are needed to
differentiate between remitting and chronic sarcoidosis.
Finding a specialist
Support and coping
Research
Because of the many uncertainties
about the pathogenesis, course, and management of sarcoidosis,
the National Heart, Lung, and Blood Institute convened a working
group to identify future research directions and opportunities
for sarcoidosis. These include developing a tissue bank, using
novel methods to identify genetic factors, studying the
immunopathogenesis with human tissue and animal models,
exploring new approaches to diagnose and manage disease, and,
finally, conducting randomized controlled trials to assess new
therapies.
Frequently asked questions
Source material:
http://www.nhlbi.nih.gov/meetings/workshops/sarcoid-wkgp.htm
Glossary of terms
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