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"Lupus" is the root designation for a diverse array of illnesses that are linked together by distinctive clinical findings and characteristic patterns of polyclonal B-cell autoimmunity.
SLE:
| • | serum complement levels decrease with disease flares |
| • | vs. ESR which remains elevated during remission |
if ANA positive:
| • | Sm antigen (highly specific but not sensitive) |
DLE:
| • | ~ 5% of patients who present with classic DLE lesions will subsequently develop SLE |
| • | ~ 25% of patients with SLE develop DLE lesions at some point; such patients tend to have less severe forms of SLE |
| • | 30-40% ANA (+) but <5% with ANA >1:320 |
SCLE:
| • | extensive skin disease but limited systemic disease |
| • | ~ 50% of SCLE patients meet the ACR criteria for SLE, however only 10-15% develop severe manifestations such as nephritis, CNS disease, systemic vasculitis |
| • | the serious criteria of SLE are uncommon; the clinical skin lesions are the distinctive feature |
| • | 60-80% ANA (+); practically all (70-90%) have anti-Ro (SS-A) and anti-La (SS-B) antibodies |
| • | drug-induced until proven otherwise |
LUPUS PROFUNDUS:
| • | 70-75% ANA (+) (dsDNA uncommon) |
| • | ~ 50% have evidence of SLE, but the systemic features tend to be less severe (similar to DLE) |
Mixed connective tissue disease
| • | controversial entity that combines features of scleroderma, lupus, and dermatomyositis |
| • | some say that this is merely a form of SLE, but high titer of antinuclear ribonucleoprotein antibodies (U1RNP) serves as a distinguishing marker for MCT |
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