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Sarcoidosis |
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Sarcoidosis is a chronic granulomatous disease
of unknown cause, in which many tissues are
infiltrated by non-caseating granuloma.
It is slightly more common in women than in men, and most patients present
before the age of 40 years old.
The organs and systems that are most commonly involved clinically are the
lymphoreticular
system, the lungs, skin, eyes and the brain, although histological examination
in sarcoidosis
shows asymptomatic granulomas in many other organs and tissues, such as the
heart,
skeletal muscle, lacrimal glands and gastrointestinal tract.
As so many systems and organs are involved, the clinical presentation patterns
are wide
and varied; there are also marked differences in the clinical expression of the
disease
on a geographical and racial basis.
The aetiology and pathogenesis are completely unknown, although numerous
immunological
abnormalities can be detected in patients with sarcoidosis; however, these may
be an effect
of the disease rather than the cause.
Nevertheless, in lung involvement particularly, it is thought that one important
factor is
an enhanced cell-mediated immune response.
The granulomatous infiltrate of sarcoidosis may be seen in most tissues.
Lymphoreticular involvement in sarcoidosis is manifest as enlarged lymph nodes
The lymph nodes that are most commonly enlarged in sarcoidosis are the
intrathoracic lymph
nodes at the hilum of the lung. The enlargement of these nodes is invariably
bilateral and
almost symmetrical, and can be associated with diffuse pulmonary infiltration.
Sarcoid
enlargement of peripheral nodes, such as the axillary or cervical nodes, is less
common.
The spleen is histologically involved in many patients, but the enlargement of
the spleen
is clinically manifest in only about 5% of cases in Caucasians; it is more
common in Afro-Caribbeans,
probably being manifest in about 15% of cases.
Massive splenomegaly may be associated with secondary haematological features
such as pancytopenia.
Lung involvement in sarcoidosis is common, and is responsible for much of the
morbidity
In addition to the bilateral hilar lymphadenopathy, there is frequently a
diffuse pulmonary
infiltration which leads to a restrictive ventilatory defect and reduced gas
transfer.
The lung shows interstitial infiltration by typical sarcoid granulomas in the
early stages,
but these eventually heal by fibrosis.
Much of the permanent pulmonary damage, whether structural or functional, is the
result
of progressive pulmonary interstitial fibrosis.
Skin lesions in association with sarcoidosis are very common.
Skin manifestations occur in sarcoidosis in about one-quarter to one-third of
all cases.
There are two main patterns of involvement:
1 Erythema nodosum presents characteristic, tender, red or purple
subcutaneous lumps, usually on the shins and thighs, sometimes accompanied by
fever and
malaise, and frequently by associated arthralgia. It is an nflammatory lesion
of the subcutaneous fat, usually associated with inflammation of a large vein.
Although
occasional giant cells are seen in relation to necrotic fat, true sarcoid
granulomas are not seen. This pattern is particularly associated with the
bilateral hilar lymphadenopathy pattern in the thorax, and is said to have a
good prognosis.
2 Sarcoid granulomas in the skin may have several clinical manifestations,
including brown papules
(sometimes associated with hair follicles, leading to hair loss),
reddish/brown fixed nodules and plaques, and a characteristic pattern called
lupus pernio. In this pattern, which is associated with severe systemic
involvement
(including the nasal passages, lung and eye), there are persistent,
rubbery, purple shiny plaques on the face, the tip of the nose
and the ends of fingers and ears.
Eye involvement in sarcoidosis is a common presenting symptom, particularly in
women
The most common type of ophthalmic involvement in sarcoidosis is an acute
uveitis.
This is often transient and mild, and is particularly associated with erythema
nodosum
and bilateral hilar lymph node enlargement.
It is probable that uveitis occurs in over a quarter of all cases of sarcoidosis,
but is subclinical in the majority.
More severe eye involvement occurs in chronic uveitis, which is persistent and
is more likely to lead to permanent impairment of vision. It is usually
associated with more
severe sarcoidosis, e.g. with extensive pulmonary infiltration and fibrosis,
or with cutaneous lupus pernio.
Involvement of the central and peripheral nervous system in sarcoidosis is
important
and often underdiagnosed
Neurological involvement occurs in at least 10% of patients with sarcoidosis,
and is particularly common in patients with diffuse pulmonary infiltration and
eye lesions.
Sarcoid granulomas that are developing and proliferating in the nervous system
can produce
a wide range of clinical effects, which are dependent on their location;
some of the more common are:
• Chronic meningitis with cerebrospinal fluid abnormalities and non-caseating
granulomas in the meninges.
• Cranial nerve lesions, often as a result of chronic sarcoid meningeal
inflammation at the base of the brain.
• Space-occupying lesions in the cerebral hemispheres, pituitary or
hypothalamus.
• 'Mononeuritis multiplex', due to the involvement of many peripheral nerves. |
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We give here simplified and accurate information about the disease
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