甲基丙二酸尿症伴同型半胱氨酸尿症的眼部表现

Ophthalmic manifestations of methylmalonic aciduria accompanied with homocystinuria

甲基丙二酸尿症伴同型半胱氨酸尿症是常染色体隐性遗传病,表现为先天性维生素B12代谢异常,分为cbl C、cbl D、cbl F三种亚型,以cbl C最多见。确诊方法为气相色谱-质谱和串联质谱检查,皮肤成纤维细胞酶活性及互补实验和基因突变分析可明确分型。早发型1岁内发病,多累及眼部,常伴有视力下降、眼球震颤、斜视、视网膜及黄斑病变、视神经萎缩、电生理异常等表现。迟发型4岁后发病,偶累及眼部,症状较轻。眼部病变发病机制可能与高半胱氨酸水平、氧化应激及神经系统发育异常有关。眼科治疗主要为对症治疗,早期补充蛋氨酸或谷胱甘肽等抗氧化剂可能有助于治疗或缓解视网膜病变。目前我国缺少对此病患者行常规眼科检查。建立科室间合作及早期规律眼科检查对患儿视力等预后有特殊意义。

Methylmalonicaciduia（MMA） accompanied with homocystinuria is a rare autosomal-recessive with congenital metabolic disorder of Vitamin B12.There are three subtypes,cbIC,cbID,cbIF,in which cbIC is the most common one.The diagnostic tests are tandem mass spectrometry and gas chromatography-mass spectrometry.Tests for activity of enzyme in fibroblasts from skin,complementary assay and genetic analysis can be used to make the subtype clear.Early-onset patients,defined by onset of symptoms before the age of 1 year,may have severe ocular involvement,including visual loss,nystagmus,strabismus,retinopathy,maculopathy,optic atrophy,abnormal electroretinography.Late-onset patients,defined by onset of symptoms after the age of 4year,rarely have ocular manifestations.The pathogenesis of the ophthalmic symptoms may be related to the high level of homocystine,oxidative stress and the abnormal development of nervous systems.The treatment for MMA accompanied with homocystinuria is mostly symptomatic based.Ophthalmic treatment is limited.Early supplement of methionine,GSH or other antioxidants may be helpful for retinopathy.There is no standard ophthalmological examination for those patients in China.It is critical to set up inter-departmental cooperation and early stage examination for the treatments and outcomes of the patients.