A. Hamad 1 , R. Clark 1 , J. Singh 1 ; 1 Nassau University Medical Center, Eastmeadow, New York LEARNING OBJECTIVES: 1-deep venous thrombosis (DVT) can cause of fever of unknown origin (FUO). 2-the importance of computed tomography of the abdomen during work up for FUO.3-AIDS is associated with high incidence of thrombosis. CASE INFORMATION: A 45 years old Haitian female presented with generalized weakness, weight loss, and low-grade fever. She had a history of AIDS with wasting syndrome and cerebral toxoplasmosis, and recurrent deep venous thrombosis in the lower extremities. She had a temperature of 100 0F, with no swelling in the lower extremities. Plain radiograph of the chest and Urinalysis were normal. Blood, stool, and urine cultures were negative. Stool for Clostridium difficile, ova and parasite, Cryptosporidium, acid-fast bacilli and Isospora belli was negative. Sputum for acid-fast bacilli smear and culture was negative. Hepatitis profile was negative. Sputum for acid-fast bacilli and Pneumocystis carinii were negative. Few days later, she complained of severe perineal pain, rectal exam was very painful and frank blood was found on a gloved finger. Sigmoidoscopy was not done because of the pain. She was treated for an anorectal fissure and the pain improved after few days but she continued to have fever. Computed tomographic scan of the head with contrast and cerebrospinal fluid analysis were unremarkable. Computed tomography of the abdomen was done as work up for FUO. It showed massive thrombosis extending from the right renal vein to the inferior vena cava up to the liver. Hematologic work up was significant for decreased total protein S (28%) with normal protein C (64%) and antithrombin III (102%). Anticoagulation therapy was started and fever improved after more than a week. DISCUSSION: Our patient has massive thrombosis, which we think caused her prolonged fever, as an extensive work up ruled out other causes of fever. Total protein S is normal in AIDS patients with decrease in free protein S level. We believe that our patient has two separate disorders predisposing her to thrombosis (HIV infection and primary protein S deficiency). This belief depends on the fact that her total protein S was < 50% of the normal, consistent with the classic type of the hereditary protein S deficiency. Although acute thrombosis can decrease antithrombin III, it is less likely to cause a decrease in protein S or protein C. The decrease of protein S in our patient is not secondary to the thrombosis, as her antithrombin III and protein C levels were normal. We found only few reports of patients with HIV infection with protein S deficiency who presented with significant DVT. Weakness started the night before presentation and deteriorated rapidly in the next day. He reported having polydipsia and polyuria in the last few days. The patient was afebrile with blood pressure of 110/70 and heart rate of 90 bpm. Physical exam was significant for short stature (155cm) and moderate weakness of all extremities. Laboratory tests showed severe hypokalemia (1.3 meq/dl) and hypophosphatemia (1meq/dl), low bicarbonate (9 meq/dl) and normal anion gap. Arterial blood gas showed acidosis (pH = 7.12) and pCO 2 of 28 mmHg. After receiving 280 meq of potassium supplements over 16 hours his potassium level improved to 2.7 meq/dl and he regained his power completely. The patient received replacement of potassium, phosphorus, and bicarbonate for 4 days period till his numbers became normal and was discharged home on potassium citrate supplements only. Work up during hospitalization revealed urine pH repeatedly > 6.5, urine specific gravity of 1.010, urine anion gap of +40, urine pCO 2 of 50 mmHg after correction of the acidosis, daily requirement of 20 to 40 meq of bicarbonate only to maintain normal serum level, and fractional excretion of bicarbonate of 2.5% and phosphorus of 22%. Renal ultrasound revealed echogenic shadows distinct between the medulla and the cortex, consistent with calcification. DISCUSSION: Distal and proximal renal tubular acidosis are uncommon diseases. The proximal type characterized by reduction in reabsorpsion of bicarbonate while the distal type results from inability to secrete hydrogen ion. This patient represents a typical case of type I RTA (distal) with all the manifestations and complications. Short stature, severe hypokalemia with secondary paralysis and polyuria (loss of urine concentrating ability), renal calcifications, positive urine anion gap, inability to acidify the urine despite severe acidosis (oppose to proximal type), decreased urine pCO 2 (which is usually higher than the plasma because of secretion of H+ in the distal tubule that binds the bicarbonate and become CO 2 ), fractional excretion of bicarbonate of 2.5% (in proximal RTA this number is > 15%) and minimal amount of bicarbonate replacement was enough to keep normal blood level. We want physicians to be aware of this rare disease that is very easy to treat but if left untreated can have detrimental consequences.