Background and aims Systemic lupus erythematosus (SLE) is an autoimmune disease characterised by involment of various organs. Serositis is commonly seen in SLE, approximately 16% of patients with SLE have pleural or pericardial involvement. However, peritoneal involment is extremely rare, and SLE with ascites as the first manifestation is an even rarer condition.

Methods A 36 – year old woman, a housewife was admitted with progressive painless abdominal distention for a month followd by early satiety and post prandial abdominal discomfort. There was no history of medication use, abdominal surgery, trauma or infection. The physical examination finding massive ascites without evidence of organomegaly or clinical stigmata of liver disease. Laboratory data were as follows : Haemoglobin 6,8 g/dl, BUN was normal and serum albumin 2,5 g/dl. Urinalysis evidenced erythrocytes 25/ul and proteinuria ++. Puncture of ascitic fluid showed SAAG 1,1, total leukocyte count of 370 (PMN 10%,MN 90%), There is no bacterial growth and negative smear for malignancy. CT Abdomen revealed massive pelviabdominal free ascites

Results Patient diagnosed as lupus peritonitis treated with methylprednisolone and cyclosporin with substantial improvement of her condition.

Conclusions Lupus peritonitis as the initial SLE manifestation is rare, we described a case of SLE who presented with persistent massive unexplained ascites with good response to immunosuppressive therapy.