Antibodies to the extractable nuclear antigens (ENA) in Pakistani patients with systemic rheumatic disease.

Autoantibodies to the saline extracts of cells are being used as diagnostic and prognostic markers in the investigation of patients with suspected systemic rheumatic disease. These are also called antibodies to the extractable nuclear antigens or anti ENA antibodies. We used saline extracts of human spleen cells and rabbit thymus extract to detect six subtypes of anti ENA antibodies, namely anti SSA (anti Sjogren's syndrome A), anti SSB (anti Sjogren's syndrome B), anti RNP (anti Ribonucleoprotein), anti Sm (anti Smith), anti Jo-1 (anti Jo-1) and anti Scl 70 (anti Systemic sclerosis 70) antibodies. Two hundred and thirty-seven patients' sera were screened in the department of Immunology, Armed Forces Institute of Pathology (AFIP), Rawalpindi, over a period of 16 months. Fifty-seven were positive for auto antibodies, of which 26 had anti SSA antibodies, 12 anti SSA+ anti RNP+ anti Sm antibodies, 7 anti RNP+ anti Sm antibodies, 6 anti SSA+ anti SSB antibodies, 5 anti SSA+ anti RNP antibodies while one patient showed only anti RNP antibody. The detection of the anti ENA antibodies was specially helpful in diagnosing patients with systemic lupus erythematosis presenting with atypical features and with mixed connective tissue disease.