Antibodies against double stranded DNA and smooth muscle antigens are virtually diagnostic of:

Ans. b (Systemic Lupus Erythematosus). (Ref. Robbin's Pathologic Basis of Disease 7th/131: H 18th/Table 319-1)Autoantibodies in Systemic Lupus Erythematosus (SLE)AntibodyPrevalence, %Clinical UtilityAntinuclear antibodies98Best screening test; repeated negative tests make SLE unlikelyAnti-dsDNA70High titers are SLE-specific and in some patients correlate with disease activity, nephritis, vasculitisAnti-Sm25Specific for SLE; no definite clinical correlations; most patients also have anti-RNP; more common in blacks and Asians than whitesAnti-RNP40Not specific for SLE; high titers associated with syndromes that have overlap features of several rheumatic syndromes.Anti-Ro (SS-A)30Not specific for SLE; associated with sicca syndrome, predisposes to subacutecutaneous lupus, and to neonatal lupus with congenital heart block; associated with decreased risk for nephritisAnti-La (SS-B)10Usually associated with anti-Ro; associated with decreased risk for nephritisAntihistone70More frequent in drug-induced lupus than in SLEAntiphospholipid50Three tests available-ELISAs for cardiolipin and P 2G1, sensitive prothrombin time (Dilute Russell Viper Venom Time DRVVT); predisposes to clotting, fetal loss, thrombocytopeniaAntierythrocyte60Measured as direct Coombs' test; a small proportion develops overt hemolysisAntiplatelet30Associated with thrombocytopenia but sensitivity and specificity are not good; this is not a useful clinical testAntineuronal (includes anti-glutamate receptor)60In some series a positive test in CSF correlates with active CNS lupus.Antiribosomal P20In some series a positive test in serum correlates with depression or psychosis due to CNS lupusAlso remember: AutoantibodyAssociated disorder1Anti-IgG (rheumatoid factor)Rheumatoid arthritis2AnticentromereScleroderma (CREST)3Anti-Scl-70Scleroderma (diffuse)4AntimitochondrialPrimary biliary cirrhosis5Antigiiadin , Anti-glutaminase, Anti-reticulinCeliac disease6Anti-basement membraneGoodpasture's syndrome7Anti-epithelial cellPemphigus vulgaris8Antimicrosomal, antithyroglobulinHashimoto's thyroiditis9Anti-Jo-1Polymyositis, dermatomyositis10Anti-SS-A (anti-Ro)Sjogren's syndrome11Anti-SS-B (anti-La)Sjogren's syndrome12Anti-Ul RNP (ribonucleoprotein)Mixed connective tissue disease13Anti-smooth muscleAutoimmune hepatitis14Anti-glutamate decarboxylaseType 1 diabetes mellitus15c-ANCAWegener's granulomatosis16p-ANCAOther vasculitides17Antisaccharomyces cervicaeCrohn's disease18Anti-kuSLE