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Systemic Lupus
Erythematosus |
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This is a very common (though frequently
undiagnosed)condition in the general population, particularly
common in young and middle-aged women. It is one of the so-called 'connective
tissue disorders'
in which patients produce antibodies to a very wide range of their own tissues
('autoantigens').
The cause is unknown, but it has been postulated that the stimulus to the
production of the abnormal
autoantibodies may be sensitizing drugs or chemicals, or unidentified viral
infection. Drugs and chemicals
have been implicated because of the known development of SLE following the use
of many drugs,
particularly hydralazine.
Many tissues and organs are involved in SLE, but synovial joints, skin, kidneys
and brain
are the major target organs
The diagnosis of SLE is based on a combination of clinical features and the
result of laboratory
investigation, primarily the identification of the autoantibodies, and
particularly those
antibodies directed against nuclear DNA.
As so many different organs and tissues may be involved, the ways in
which the disease can present are many and varied
The range of features that can occur in SLE is shown well by the American
Rheumatism Association List of Diagnostic Criteria for SLE (in order of
specificity):
• Discoid skin rash.
• Renal abnormality (lupus nephritis).
• Neurological disorder.
• Evidence of immunological disorder.
• Malar skin rash
• Haematological disorder.
• Skin photosensitivity
• Serosal inflammation.
• Oral ulceration.
• Presence of antinuclear antibody.
• Arthritis.
Oral mucosal lesions in SLE produce superficial erosions and ulcers
Skin rashes of various types occur in about 80% of all patients with systemic
lupus
One of the most common tissues affected in SLE is the skin.
The most common patterns of skin rash are:
• Chronic discoid LE: round ('discoid'), red scaly telangiectatic plaques,
usually on face and scalp, and
less commonly on the hands. Follicular plugging with keratin is common,
particularly in the scalp and facial
lesions. The lesions heal from the centre, with the skin becoming atrophic,
often with loss of pigment.
Involvement of the scalp may lead to patchy hair loss this is a cause of
scarring alopecia.
• Malar skin rash: a symmetrical, slightly raised red erythematous rash on the
cheeks and across the bridge
of the nose. The characteristic distribution of broad patches on the cheeks
joined by a narrower band
across the nose has led to this being called the 'butterfly' rash.
• Photosensitivity reactions: rashes in light-exposed areas, worse when there
has been increased sun
exposure, may be of either of the above malar or discoid patterns, but may also
be non-specific. Direct
immunofluorescence of sun-exposed, but non-lesional, skin shows IgG, IgM and
complement in the epidermal
basement membrane in patients with SLE, irrespective of the clinical pattern of
the skin disease.
These represent immune complex deposits on the dermal side of the
basement membrane, within the intercellular matrix and between collagen fibres.
• Vasculitic skin lesions: these occur as either an acute purpuric neutrophilic
vasculitis
in the upper dermis, or a lymphocytic vasculitis producing slightly raised
erythematous patches, and are important features of skin rashes in lupus;
their significance is often missed because the rashes do not conform to the
classical
discoid or malar types described above.
The SLE variant that is known as mixed connective tissue disease (MCTD) has skin
lesions less commonly
than classic SLE, but many patients have a non-specific lymphocytic vasculitis
at some stage in the illness,
and eventually develop Raynaud's phenomenon.
Immunological investigation of suspected SLE
Neurological and psychiatric disorders are common in SLE, and may be the
presenting symptom
The most common feature of neurological involvement in SLE is a non-organic
psychiatric disorder of unknown
cause; occasional cases that come to autopsy show either acute neutrophilic or
lymphocytic vasculitis
in the brain.
Patients may also have a wide range of organic brain disorders,
such as focal demyelination,
microinfarction and neuronal loss, leading to a variety of symptoms. Grand mal
epileptic seizures
are an important clinical manifestation of cerebral lupus.
Vascular occlusion is the result of antiphospholipid antibodies causing platelet
aggregation.
It is important to remember that some of the neurological manifestations in SLE
may be the result of the treatment
rather than the disease, particularly corticosteroid therapy.
Haematological abnormalities are common in SLE
Patients with SLE frequently have haematological abnormalities, some having an
unknown cause, and
others having an autoimmune mechanism.
• Normocytic hypochromic anaemia.
• Autoimmune haemolytic anaemia (approximately 10% of cases),
with red-cell antibodies and positive Coombs test.
• Reduced peripheral white cell count, usually due to
disproportionate reduction of lymphocytes (lymphopenia).
• Thrombocytopenia, sometimes associated with the presence of
anti-platelet antibodies.
• Predisposition to thrombosis, particularly if there are
anticardiolipin/lupus anticoagulant antibodies.
Musculoskeletal symptoms may be the earliest presenting feature of SLE
SLE frequently presents clinically with musculoskeletal symptoms.
Joint pain and
other symptoms of arthritis
occur in about 90% of all patients, and may precede the recognition of SLE by
some years.
The main
rheumatological disorders of SLE are arthritis, bone disease and myalgia.
Arthritis, which is misdiagnosed sometimes as rheumatoid arthritis or
asymmetrical polyarticular
arthritis, usually begins in the fingers, wrists and knees. Avascular bone
necrosis may contribute
to the arthropathy. The synovial surfaces may show fibrin deposition, and the
articular cartilage shows
changes similar to those seen in mild rheumatoid arthritis.
Bone disease usually presents as disproportionately severe osteoporosis for the
age. It is difficult to
separate the osteoporosis due to SLE from that due to the corticosteroids used
in treatment. Avascular bone
necrosis is common in SLE, appearing to be polyarticular, and usually being
associated with the joints
showing the most severe arthritis.
Myalgia, in the form of pain in skeletal muscles, is a very common feature of
SLE, and is frequently
neglected clinically since it is difficult to dissociate from the pain due to
coexisting arthritis.
Muscle biopsy in patients with significant myalgia frequently shows a
lymphocytic vasculitis.
Kidney involvement in SLE is common, and is an important cause of morbidity and
mortality
Renal involvement in lupus is common, and the severity can vary from minor
abnormalities
(such as asymptomatic albuminuria) to severe glomerular disease leading to
renal failure. The main abnormalities in renal involvement in SLE are in the
glomerulus, where
there can be a wide range of structural abnormalities.
There may also be extraglomerular vascular abnormalities and tubular damage,
particularly interstitial nephritis.
Lupus nephritis may mimic other forms of glomerular disease by showing the
following patterns: focal
segmental mesangial glomerulonephritis, focal segmental proliferative
glomerulonephritis with tuft damage,
membranous nephropathy, and membranoproliferative pattern of lupus nephritis.
The basis of the glomerular damage in all patterns is the deposition of immune
complexes
in the glomerulus. The complexes may be deposited in the basement membrane
(leading to basement membrane
thickening), or in the mesangium (leading to mesangial expansion);
immunofluorescence methods show that
the immune complexes contain three types of immunoglobulin, IgG, IgA and IgM,
and two
types of complement, C3 and C1q.
The detection of this 'full house' of immunoglobulins and complement factors,
together with the particular
locations of the immune complexes in relation to the glomerular basement
membrane, are important
factors in distinguishing lupus glomerulonephritis from non-lupus patterns. |
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