An abdominal xray showed a normal bowel gas pattern with no renal calculi. He was presumed to have radiolucent nephrolithiasis and was advised to follow-up closely. Five days later, he presented to the emergency room with unremitting flank pain, new suprapubic pain, dysuria and fevers to 103±104 F. His only medications were ibuprofen and percocet (prescribed recently for his flank pain). On exam, he appeared uncomfortable, had a T 99.2 F, oral thrush, and bilateral cervical/axillary lymphadenopathy. His abdomen was soft, mildly distended, and diffusely tender to palpation, particularly in the suprapubic area. He had scattered papules with central umbilication on his face, buttocks, and thighs. Laboratory studies were significant for a WBC 5.6, hemoglobin 11.9, creatinine 2.6, AST 124, ALT 158, alkaline phosphatase 627, and total bilirubin 1.5. Abdominal CT scan showed bulky retroperitoneal and pelvic lymphadenopathy, bilateral hydronephrosis, and a circumferentially thickened bladder wall. Bone marrow biopsy and bladder wall biopsy confirmed the diagnosis of stage IV immunoblastic non-Hodgkin's lymphoma involving the bone marrow, GI tract, liver, spleen, and bladder. HIV was positive with a CD4 count of 138 and a viral load of >500,000. IMPLICATIONS/DISCUSSION: Non-Hodgkin's lymphoma occurs in 10-30% of AIDS patients, the most common type being high-grade diffuse large B cell (immunoblastic variant) or Burkitt's-like. Patients usually present with stage IV disease and frequently have involvement of the bone marrow, CNS, liver, and gastrointestinal tract. Although HIV associated systemic lymphoma frequently presents with rapid nodal enlargement and B symptoms, it has no pathognomonic features. This previously healthy male had HIV risk factors as well as molluscum contagiosum and oral thrush that suggested the diagnosis of HIV infection. In addition to chemotherapy, immune reconsitution with highly active anti-retroviral would be necessary for effective treatment.