[A case of crescentic poststreptococcal acute glomerulonephritis (PSAGN) accompanied by membranous nephropathy].

In 2010, a 71-year-old man was referred to our hospital because of mild proteinuria and hematuria. At that time, he had been asymptomatic. Three months later he noticed macroscopic hematuria, followed by general malaise, and then anorexia. He was admitted for acute kidney injury (serum creatinine 2.7 mg/dL), marked proteinuria (4.35 g/gCr), and elevated C-reactive protein (7.21 mg/dL). Some vesicles were noted on the soft palate, and a throat culture yielded a growth of group A beta-hemolytic streptococci. Antistreptolysin O and antistreptokinase titers were elevated, but serum complement levels were within normal limits. Antineutrophil cytoplasmic antibodies (ANCA) directed against elastase and bactericidal permeability increasing protein (BPI)were positive. The renal function and inflammation did not improve despite oral antibiotic therapy. Pathological examination of a renal biopsy specimen revealed diffuse crescent formation, numerous subepithelial dome-shaped deposits (humps), and prominent endocapillary proliferation. Furthermore, a focal and segmental spike appearance was seen, with deposits smaller than humps. There was a striking clinical improvement after steroid pulse therapy followed by oral prednisolone. The features of this case strongly suggest crescentic PSAGN accompanied by pre-existing membranous nephropathy.