Case Presentation: A previously healthy 35-year-old woman presented with fever, dizziness, and weakness for 1 day. Three weeks prior, she had back pain and difficulty taking deep inspirations that was treated with a 10-day course of levofloxacin. The pain subsided; however, she noticed frothy urine. Other symptoms included a 30-pound weight loss in 4 months and gingival bleeding after a dental cleaning. She became increasingly dizzy and developed a fever to 38.3° Celsius on the final day of antibiotics which led her to come to the hospital. On admission, temperature was 37.7° C, blood pressure was 146/81 mmHg, heart rate was 96 beats per minute, respiratory rate was 18 breaths per minute, and oxygen saturation was 98% on room air. Her lungs were clear to auscultation, and she had no costovertebral angle tenderness. Laboratory evaluation revealed a white blood cell count of 4,400/mcL, hemoglobin of 7.9 gm/dL, hematocrit of 25.8%, and platelet count of 120,000/mcL. Blood urea nitrogen was 20 mg/dL, creatinine was 2.09 mg/dL, and alkaline phosphatase was 354 unit/L. Urinalysis revealed a urine protein of 151 mg/dL and urine creatinine of 292 mg/dL. Work-up including blood cultures, chest X-ray, and urinalysis was negative for infection. Computed tomography of her chest, abdomen, and pelvis was notable for bilateral nephromegaly. Her fevers persisted for 3 days with a maximum temperature of 39.6° C. Additional laboratory studies, including HIV, dsDNA, C3, C4, ANA, ANCA, and hemoglobin electrophoresis, were unremarkable. Alkaline phosphatase was down trending initially, then started to up trend and she developed a transaminitis on Day 5. Ultrasound abdomen revealed a coarsened liver and gall bladder sludge. Her free kappa light chains were found to be elevated at 36 mg/L, prompting pursuit of a bone marrow biopsy. On day 8, results of the bone marrow biopsy were positive for B-cell acute lymphoblastic leukemia/lymphoma. She was started on daunorubicin, vincristine, and leuprolide chemotherapy which led to resolution of her kidney disease.
Discussion: Bilateral nephromegaly is a rare finding with a specific differential diagnosis. It usually represents an autoimmune or infiltrative process if there is no obvious obstruction. Common autoimmune diseases included in the differential are lupus, acute glomerular nephritis, acute interstitial nephritis, and renal vasculitis. The differential diagnosis for infiltrative processes includes amyloidosis, multiple myeloma, and hematologic malignancies. Other possible etiologies include sickle cell disease, thalassemia, and HIV nephropathy. In this case, her persistent fevers were suspicious for malignancy. This patient had extensive work-up which included a bone marrow biopsy after elevated free kappa light chains were noted.
Conclusions: The presentation of bilateral nephromegaly and proteinuria should prompt a work-up that includes consideration for autoimmune, infiltrative, and infectious processes. Close attention to patient history and physical exam in combination with a detailed laboratory workup should be done to help narrow the differential and reach a definitive diagnosis.