Division of Nephrology and Hypertension, Mayo Clinic Hospital Jacksonville, Jacksonville, Florida, USA.
Department of Pathology, Mayo Clinic Hospital Jacksonville, Jacksonville, Florida, USA.
BMJ Case Rep. 2021 Feb 18;14(2):e239868. doi: 10.1136/bcr-2020-239868.
Fibrillary glomerulonephritis (FGN) and complement 3 glomerulopathy (C3G) are rare forms of glomerulonephritis with distinct aetiologies. Both FGN and C3G can present with nephritic syndrome. FGN is associated with autoimmune disease, dysproteinaemia, malignancy and hepatitis C infection. C3G is caused by the unregulated activation of the alternative complement pathway. We present a rare case of diffuse necrotising crescentic glomerulonephritis with dominant C3 glomerular staining on immunofluorescence-consistent with C3G-but electron microscopy (EM) findings of randomly oriented fibrils with a mean diameter of 14 nm and positive immunohistochemistry for DNAJB9-suggestive of FGN. To the best of our knowledge, this is the first reported case of FGN to show dominant C3 glomerular deposits. This case report reaffirms the utility of EM in the evaluation of nephritic syndrome and highlights the value of DNAJB9-a novel biomarker with a sensitivity and specificity near 100% for FGN.
纤维状肾小球肾炎 (FGN) 和补体 3 肾小球病 (C3G) 是两种罕见的肾小球肾炎，具有不同的病因。FGN 和 C3G 均可表现为肾病综合征。FGN 与自身免疫性疾病、副蛋白血症、恶性肿瘤和丙型肝炎感染有关。C3G 是由替代补体途径的不受调节的激活引起的。我们报告了一例罕见的弥漫性坏死性新月体肾小球肾炎，免疫荧光表现为 C3 肾小球染色占优势，与 C3G 一致 - 但电子显微镜 (EM) 发现随机取向的纤维，平均直径为 14nm，并且 DNAJB9 的免疫组化阳性 - 提示 FGN。据我们所知，这是首例报告的表现为 C3 肾小球沉积优势的 FGN 病例。本病例报告再次证实了 EM 在评估肾病综合征中的实用性，并强调了 DNAJB9 的价值，这是一种新型生物标志物，对 FGN 的敏感性和特异性接近 100%。
