Acute renal failure as the initial presentation of T-lymphoblastic lymphoma: A case report.

T-lymphoblastic lymphoma/leukemia (T-LBL) is a rare and aggressive hematologic malignancy characterized by a neoplastic proliferation of immature T lymphocytes that is restricted to nodal/extra-nodal sites with minimal involvement of bone marrow. While T-LBL is the second most frequent subtype of pediatric non-Hodgkin lymphoma, primary renal involvement in T-LBL is exceedingly rare and can pose a significant diagnostic challenge. We present the case of an 11-year-old male who initially presented with new-onset seizure, hypertensive crisis, and acute renal failure. Renal ultrasounds demonstrated enlarged kidneys with loss of corticomedullary differentiation suggestive of medical renal disease. A kidney biopsy was performed, revealing an atypical interstitial T-cell infiltrate with diffuse expression of CD4, CD8, and TdT, raising concern for T-cell acute lymphoblastic lymphoma (instead of leukemia) (T-ALL/LBL). A subsequent bone marrow biopsy was negative, and no other sites of involvement were identified on PET/CT, so chemotherapy was deferred until the diagnosis could be confirmed. The patient re-presented 2 months later with visual changes and diffuse leptomeningeal enhancement on MRI. Repeat kidney biopsy with flow cytometry demonstrated a population of aberrant T cells with CD4/CD8 co-expression. A repeat bone marrow biopsy contained < 1% blasts, and no aberrant lymphocytes were detected in peripheral blood. CT scan revealed new retroperitoneal adenopathy with infiltrative disease involving kidneys, pancreas, adrenal glands, and liver, consistent with stage IV T-LBL.Kidney involvement in acute LBL is uncommon, and renal failure due to leukemic infiltration is rarely reported. This case underscores the importance of performing kidney biopsies in cases of unexplained acute renal failure and considering lymphoma in the differential for interstitial nephritis, even in the absence of abnormal hematological findings.