顕微鏡的多発血管炎にMPO-ANCA関連肥厚性硬膜炎を合併し右眼の光覚を消失した1例

A case of loss of light perception in the right eye associated with ANCA-related hypertrophic pachymeningitis during the course of microscopic polyangiitis

要約　目的：顕微鏡的多発血管炎（MPA）の経過中にMPO-ANCA関連肥厚性硬膜炎を発症し，右眼の光覚を消失した1例を報告する。

症例：82歳，女性。9年前にMPO-ANCAが高値で腎生検の結果MPAと診断され，MPAの加療中であった。1か月前より右視力低下を自覚し受診した。

所見と経過：矯正視力は右光覚なし，左1.2で，相対的瞳孔求心路障害は右眼で陽性であった。眼底写真およびフルオレセイン蛍光眼底造影検査で，両眼ともに異常所見はなかった。血液検査で，MPO-ANCAは基準値内であり，CRPは陰性であった。頭部造影MRI検査で肥厚性硬膜炎の所見に加え，右眼窩先端部の造影増強がみられ，右眼窩先端部炎が視力障害の原因と考えられた。ステロイドセミパルス療法を2クール施行し，右視力は（0.7）に改善し，右眼ゴールドマン視野も中心約15°の中心暗点（I/3e〜I/4e視標）は残ったが，周辺視野は回復した。

結論：MPO-ANCAが基準値内であっても，MPAの経過中にANCA関連肥厚性硬膜炎を発症し，重篤な視力障害を引き起こす可能性がある。

Abstract　Purpose：To report a case of loss of light perception in the right eye（RE）associated with anti-neutrophil cytoplasmic antibody（ANCA）-related hypertrophic pachymeningitis during the course of microscopic polyangiitis（MPA）.

Case：An 82-year-old woman, diagnosed with MPA after a renal biopsy 9 years ago due to high myeloperoxidase（MPO）-ANCA levels, has been treated for MPO-ANCA positive MPA. The patient presented to our hospital with decreased visual acuity in the RE one month before the presentation.

Findings and clinical courses：The corrected visual acuity was no light perception in the RE and 1.2 in the left eye. Relative afferent pupillary defect was detected in the RE. Funduscopy and fluorescein angiography showed no abnormal findings. In a blood test, serum MPO-ANCA levels were within normal limits and C-reactive protein was negative. Brain contrast-enhanced magnetic resonance imaging revealed an enhanced lesion in the right orbital apex in addition to findings of hypertrophic pachymeningitis, suggesting that orbital apex inflammation may lead to loss of visual acuity. After two courses of steroid semi-pulse therapy, her corrected visual acuity improved to 0.7 in the RE. Goldmann perimetry revealed only about 15 degree central scotoma with I 3e to I 4e and recovery of peripheral visual field in the RE.

Conclusions：ANCA-related hypertrophic pachymeningitis that causes severe loss of visual acuity can occur during the course of MPA, even though serum MPO-ANCA is within normal limits.