A case of ANCA-negative pauci-immune crescentic glomerulonephritis with lung adenocarcinoma with mediastinal involvement successfully treated by corticosteroid and radiation therapy.

Pauci-immune crescentic glomerulonephritis (PICGN) is one of the pathologies causing rapidly progressive glomerulonephritis, often associated with anti-neutrophil cytoplasmic antibody (ANCA); however, in 10-30% of cases, ANCAs are negative. While a relatively large number of cases of ANCA-positive PICGN complicated with malignancy have been previously reported, the number of cases of ANCA-negative PICGN with malignancy is limited. The prognosis for such cases was poor, and many patients died within a relatively short period. Here, we report the case of ANCA-negative PICGN complicated with malignancy successfully treated by corticosteroid and radiation therapy. A 63-year-old Japanese man was admitted to our hospital due to spiking fevers in the previous 3 months. Based on the findings of imaging and pathological tests, he was diagnosed with locally advanced lung adenocarcinoma with mediastinal involvement. After admission, his renal function rapidly deteriorated, and urinalysis showed heavy proteinuria. In serological tests, serology for autoantibodies, including ANCAs, was negative. The kidney biopsy revealed PICGN with prominent endocapillary proliferation. We administered corticosteroid therapy for glomerulonephritis and subsequent radiation therapy for lung carcinoma, both of which were effective. He has been alive without progression of malignancy or kidney disease for 5 years after discharge. In patients with malignancy presenting with acute deterioration of kidney function, although infrequent, one of the conceivable pathological conditions to consider is ANCA-negative PICGN associated with malignancy. In such cases, even with negative antibodies such as ANCA, pathological examination is warranted, and a combination of anti-tumor therapy and immunosuppressive therapy is expected to be effective.