Systemic Lupus Erythematosus (SLE)
The manifestations are protean, and there is no characteristic or pathognomonic finding. Instead, this disease is diagnosed by finding suggestive serologic and clinical findings. Findings may include:
Genetic factors: tends to run in families; association with HLA Dr-2 and Dr-3; more common in young women (especially African-American).
Drugs can produce "drug-induced" SLE: list includes procainamide, hydralazine, isoniazid, d-penicillamine.
Discoid lupus erythematosus (DLE): a benign disease with skin involvement; ANA positive in only a third (but some of these go on to SLE).
Mixed Connective Tissue Disease (MCTD)
A wastebasket category for patients who do not clearly fit into other categories. There are features similar to SLE, scleroderma, and polymyositis. Most patients are middle aged females. Characteristic feature is a speckled ANA pattern.