抗糸球体基底膜抗体陽性糸球体腎炎に極小変化疾患が重なったネフローゼ症候群の一例

Nephrotic syndrome due to minimal-change disease superimposed on anti-glomerular basement membrane antibody positive glomerulonephritis; a case report.

• Yuko Shibata
• Kazuhito Fukuoka
• Riyo Yokota
• Heryon Lee
• Hikaru Sayo
• Noriko Ikegaya
• Kiyotaka Mori
• Jin Yamamoto
• Aya Isomura
• Kiyotaka Nagahama
• Hiroaki Shimoyamada
• Takahisa Kawakami
• Yoshinori Komagata
• Shinya Kaname

抄録

背景:

抗GBM糸球体腎炎（抗GBM GN）の腎機能の予後は極めて悪く、腎機能障害が重度に進行した場合には改善を期待することは困難です。また、一度積極的な治療で疾患活動性をコントロールできれば、再発はまれであることも知られています。当院では、重度の腎機能障害から改善して再発した抗GBMのGNを経験しました。原因として考えられるのは、ミニマムチェンジ病（MCD）によるネフローゼ症候群の重症化であった。

BACKGROUND: The prognosis for renal function in anti-GBM glomerulonephritis (anti-GBM GN) is extremely poor, and when renal impairment progresses severely, it is difficult to expect improvement. In addition, it is also known that once the disease activity can be controlled by aggressive treatment, its recurrence is rare. We experienced an anti-GBM GN that improved from severe renal dysfunction and relapsed. A possible cause was the superimpose of nephrotic syndrome due to minimal change disease (MCD).

事例紹介:

30歳の男性が全身倦怠感、発熱、乏尿、腎機能障害で当院に入院した。臨床検査値は血清クレアチニンが6.6mg/dlと高く，重度の炎症（C反応性蛋白20.6mg/dl）を呈していた．血清中に抗糸球体基底膜抗体（抗GBM Ab）が検出され、抗GBM GNと診断された。高用量グルココルチコイド（GC）と血漿交換療法（PE）による治療を開始したところ，腎機能と乏尿が急速に改善し，入院から40日後に退院した．腎生検所見は抗GBM GNに適合する糸球体房に沿った線状IgGの沈着を伴う細胞クレッセントを認めたが，糸球体の3分の1程度しか認められず，まだ初期段階の疾患であることが示唆された．しかし、退院後2ヵ月後に再発し、抗GBMのAbが陽性の重度の蛋白尿のため再入院となった。2回目の入院では、高用量GCとPEにシクロホスファミド静注を併用した後、寛解に至った。腎生検所見は比較的軽度であったが，腎機能障害は急速に改善し，当院の治療により比較的急速に改善した．腎生検組織の電子顕微鏡検査では，一見正常な糸球体の鞘細胞上に有意な足底突起の消失が認められたが，電子密度の高い沈着は認められなかった．

CASE PRESENTATION: A 30-year-old man was admitted to our hospital because of general malaise, fever, oliguria and renal dysfunction. The patient's laboratory data showed serum creatinine as high as 6.6 mg/dl, and severe inflammation (C-reactive protein 20.6 mg/dl). Anti-glomerular basement membrane antibody (anti-GBM Ab) was detected in his serum, which led to the diagnosis of anti-GBM GN. Treatment was initiated with high-dose glucocorticoid (GC) and plasma exchange therapy (PE), and the patient's renal function and oliguria improved rapidly and he was discharged 40 days after admission. Renal biopsy findings showed cellular crescents associated with linear IgG depositions along the glomerular tufts compatible with anti-GBM GN, but only about one-third of the glomeruli was involved, suggesting that it still remains an early stage of the disease. However, 2 months after discharge, he had a relapse and was readmitted due to severe proteinuria with positive anti-GBM Ab. On the second admission, after high-dose GC and PE combined with intravenous cyclophosphamide, and remission was achieved. Despite the relatively minor renal biopsy findings, the patient showed rapid renal dysfunction and relatively rapid improvement with our treatment. Electron microscopy of the renal biopsy tissue showed significant foot process effacement on podocytes in the apparently normal glomeruli, without electron dense deposits.

結論:

臨床経過と腎病理学的にみて，本症例は抗GBM抗体による早期のGNと極小変化ネフローゼ症候群のまれな合併症であることが示唆された．抗GBM抗体を有する抗GBM GNとMCDの同時発症は不明であるが、インフルエンザ感染や何らかの未知の要因により発症した可能性がある。

CONCLUSION: On the basis of clinical course and renal pathology, it is suggested that the present case was a rare complication of an early stage of anti-GBM GN and minimal change nephrotic syndrome. Although the simultaneous development of anti-GBM GN and MCD with anti-GBM antibody is unclear, it might have been precipitated by influenza infection or some unknown factor.