PMC9763891_01
(A) X-ray revealed abnormal density areas (arrows) in the bilateral lower lobe of the lungs (symmetric distribution). (B) Chest CT revealed a large area of shadow (arrows) in the bilateral lower lobe of the lungs (before the treatment). (C) Chest CT revealed the shadows (arrows) in bilateral lungs improved (during the treatment). (D) Chest CT revealed the lesions disappeared (after the treatment). (E, F) Renal biopsies (HE x40) revealed glomerulonephritic fibrocellular crescents (arrows). (G) Renal biopsies revealed vascular occlusion (arrows). (H) Normal control glomerulus. (I) Clinical timeline. GC, glucocorticoid; CTX, cyclophosphamide; PE, plasma exchange.
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The chest X-ray revealed areas of abnormal density (symmetric distribution) in the bilateral lower lobes of the lungs ( Figure 1A ). Further examination revealed the following notable laboratory test findings, in chronological order: urinalysis revealed microscopic hematuria (+++) and proteinuria (++) on 14 May; renal function revealed BUN 4.85 mmol/L, Cr 81.6 micromol/L, UA 213.7 micromol/L, and C3 1,300 mg/L; inflammatory markers were slightly increased (ESR 29 mm/h and CRP 19 mg/L); ANA was present in a relatively low titer (1:80), without any antigen-specific antibodies; p-ANCA was positive and MPO-ANCA revealed 50.9 U/ml (normal <20 U/ml); PR3 and GBM were normal on 16 May; the chest CT performed on May 16 revealed an area of dense shadow in the bilateral lower lobes of the lungs, without ground-glass opacity and reticulation ( Figure 1B ), but pulmonary artery CT and PPD were normal. To ultimately establish a proper diagnosis, renal biopsies were performed as a result of the proteinuria and positive MPO and p-ANCA identified on 18 May; finally, the biopsies revealed glomerular cellular and microcellular crescents ( Figures 1E-H ). MPO and p-ANCA, and the renal biopsies, our patient was finally diagnosed with microscopic polyangiitis (MPA), and so we started immunosuppressive treatment: methylprednisolone (800 mg/day*3 days, two cycles), plasma exchange (1,500 ml/day*4 days), and IV-cyclophosphamide (CTX 800 mg/day once), followed by oral formulation of methylprednisolone (48 mg/day) and tacrolimus (4 mg daily). Methylprednisolone pulse therapy and plasmapheresis resulted in dramatic clinical and imaging improvements ( Figures 1C, D ). The clinical timeline is presented in  Figure 1I .