Crescentic glomerulonephritis associated with NK-large granular lymphocytic leukemia: A case report.

Rationale: Chronic lymphoproliferative disorder of natural killer cells is a rare heterogeneous indolent hematological disease, characterized by persistent clonal increase of mature NK cells with a typical large granular lymphocyte pattern. Chronic lymphoproliferative disorder of natural killer cells was revised to NK-large granular lymphocytic leukemia (NK-LGLL) in 2022 WHO classification. Renal involvement in NK-LGLL is extremely rare. Here, we report a woman diagnosed with NK-LGLL and nephrotic syndrome.

Patient Concerns: A 54-year-old woman had no obvious symptoms except for persistent peripheral lymphocytosis and neutropenia before kidney involvement. Then she presented with nephrotic syndrome, acute kidney injury and Epstein-Barr virus infection.

Diagnoses: Bone marrow displayed clonal increase of mature NK cells with a typical large granular lymphocyte pattern. Renal biopsy showed pauci-immune crescentic glomerulonephritis and renal infiltration by NK-LGLL after exclusion of other diseases. Pathogenic N642H mutation of STAT5B was detected by targeted exome sequencing. A319T mutation in RELN and R500W mutation in INTS1 were also identified. Hence, she was diagnosed with crescentic glomerulonephritis associated with NK-LGLL.

Interventions And Outcome: We planned to combine methylprednisolone and cyclophosphamide in the treatment of this case. Unfortunately, our patient died of severe cerebral hemorrhage shortly after the diagnosis of NK-LGLL. We had no opportunity to use immunosuppressive drugs for therapy.

Lessons: In short, we report a unique case diagnosed with crescentic glomerulonephritis associated with NK-LGLL, with pathogenic N642H mutation in STAT5B, Epstein-Barr virus infection and poor prognosis, different from typical inert type. Close monitoring of renal function is suggested for similar NK-LGLL patients.