Seventy female and three male Omani systemic lupus erythematosus (SLE) patients are described. At disease onset, 45 (62%) were under 20 years of age, and the remainder were between 20 and 44. Of all cases, 48% were familial. Over 5 years, the cumulative frequencies of autoantibodies was: antinuclear antibodies (ANA) 97%, anti-double-stranded DNA (anti-dsDNA) antibodies 92%, extractable nuclear antigen (ENA) antibodies 64%, antineutrophil cytoplasmic antibodies (ANCA) 58%, antiphospholipid (APL) antibodies 80%, and rheumatoid factor (Rf) 22%. Ribonucleoprotein (RNP) antibodies were found in 15/45 younger-onset and 2/28 older-onset patients (χ2= 6.63 P < 0.02). The mean SLE disease activity score (SLEDAI) was 13.5 + 11.4, and the cumulative frequencies of systemic involvement were: neurological 33.8%, vascular 10.4%, musculoskeletal 53.9%, renal 50.7%, dermal 80.5%, serosal 23.9%, immunological 95%, constitutional 31.3%, and haematological 26.0%. Linear regression analysis showed that high-titre ANA were predictors for pyuria (odds ratio [OR] 9.06, P=0.01). Antiextractable nuclear antigen antibodies were predictors for disease of the neurological (OR 26.3, P=0.008) and serosal (OR 27.7, P=0.005) systems, and anti-Sm antibodies for alopecia (OR 5.93, P=0.088) and hypocomplementaemia (OR 14.6, P= 0.016). Antibodies of known diagnostic utility may also give insights into the pathogenesis of SLE.
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