Shute Clare
Royal Victoria Hospital, Belfast, Northern Ireland.
BMC Ophthalmol. 2018 Sep 14;18(Suppl 1):220. doi: 10.1186/s12886-018-0859-2.
Retinal vascular occlusions are uncommon in young people and require more in-depth investigation into the cause. Studies have revealed that a high level of circulating homocysteine poses a risk for retinal vaso-occlusive events across a wide age range. This case report reflects on how the interplay of genetic mutation and vitamin deficiency can cause a pathological level of homocysteine with resultant branch retinal artery occlusion in a young patient.
A 16-year-old boy presented to eye casualty with acute inferior visual field loss in the left eye. Visual acuity remained normal at 6/6 each eye and the event was painless. Initial assessment, and retinal photography revealed a left superior hemi-field branch retinal artery occlusion with macular sparing. Given the patient's age, extensive investigation into the cause was carried out. Positive findings were of an elevated level of homocysteine as a result of vitamin B12 and folic acid deficiency as well as a genetic mutation in the MTHFR gene (encoding MTHFR enzyme which is vital in normal homocysteine metabolism). Vitamin B12 and folic acid were replaced which in turn normalized the patient's homocysteine levels. At two months, the patient's visual fields had also improved, and no further vascular event had occurred.
This case report has highlighted the link between hyperhomocysteinaemia and retinal artery occlusion. However, despite vitamin replacement being shown to normalize homocysteine levels, no evidence exists to date as to whether this will reduce the risk of further retinal vascular occlusion.
视网膜血管阻塞在年轻人中并不常见，需要对病因进行更深入的调查。研究表明，高水平的循环同型半胱氨酸在广泛的年龄范围内会引发视网膜血管阻塞事件。本病例报告探讨了基因突变与维生素缺乏之间的相互作用如何导致一名年轻患者出现病理性同型半胱氨酸水平，进而引发视网膜分支动脉阻塞。
一名16岁男孩因左眼急性下视野缺损就诊于眼科急诊。双眼视力均保持正常，为6/6，且此次发病无痛感。初步评估及视网膜照相显示左眼上半视野视网膜分支动脉阻塞，黄斑区未受累。鉴于患者年龄，对病因进行了广泛调查。阳性结果显示，由于维生素B12和叶酸缺乏以及MTHFR基因（编码对正常同型半胱氨酸代谢至关重要的MTHFR酶）发生基因突变，导致同型半胱氨酸水平升高。补充维生素B12和叶酸后，患者的同型半胱氨酸水平恢复正常。两个月时，患者的视野也有所改善，且未发生进一步的血管事件。
本病例报告强调了高同型半胱氨酸血症与视网膜动脉阻塞之间的联系。然而，尽管补充维生素已被证明可使同型半胱氨酸水平正常化，但迄今为止，尚无证据表明这是否会降低进一步发生视网膜血管阻塞的风险。
