亚甲基四氢叶酸还原酶缺陷导致学童精神分裂症

Methylenetetrahydrofolate reductase deficiency-induced schizophrenia in a school-age boy

摘要:

亚甲基四氢叶酸还原酶（MTHFR）缺陷是一种少见的常染色体隐性遗传性疾病，是高同型半胱氨酸血症的常见类型之一。该文通过对1例MTHFR缺陷导致的精神障碍的临床经过、生化特点、MTHFR 基因突变进行回顾性研究，探讨该病的临床特点与诊疗方法。患儿11岁起出现精神异常，恐惧、幻听、学习困难、入睡困难、脾气暴躁、发呆、傻笑，符合精神分裂症诊断。多种精神科药物治疗无效，休学。13岁时来院就诊，血、尿总同型半胱氨酸明显升高。血浆和脑脊液叶酸均显著降低。血液蛋氨酸水平正常。患儿MTHFR基因存在665C>T纯合突变。经亚叶酸钙、维生素B₁₂、维生素B₆、甜菜碱补充治疗1周后，患儿血清及尿液总同型半胱氨酸降至正常，病情逐步改善，3个月后复学。晚发型MTHFR缺陷合并继发性脑叶酸缺乏症的患儿可表现为精神分裂症；血液及尿液总同型半胱氨酸测定、血液氨基酸测定、血清及脑脊液叶酸测定及基因分析对患者的病因诊断非常重要；补充叶酸、维生素B₆、维生素B₁₂、甜菜碱治疗有效。

Abstract:

Methylenetetrahydrofolate reductase (MTHFR) deficiency is a rare autosomal recessive disorder. It is known that MTHFR deficiency may result in hyperhomocysteinemia, but MTHFR deficiency-induced schizophrenia has been rarely reported. Here we present the clinical course, biochemical and genetic characteristics of schizophrenia resulted from MTHFR deficiency in a school-age boy. He was 13 years old. He was admitted with a two-year history of fear, auditory hallucination, learning difficulty, sleeping problems, irascibility, drowsing and giggling. At admission, he had significantly elevated plasma and urine levels of total homocysteine, significantly decreased levels of folate in serum and cerebrospinal fluid, and a normal blood concentration of methionine. Further DNA sequencing analysis showed 665C>T homozygous mutations in the MTHFR gene. The patient was diagnosed with MTHFR deficiency-associated schizophrenia and treatment with calcium folinate, vitamin B₁₂, vitamin B₆, and betaine was initiated. After the treatment for 1 week, his plasma and urine levels of homocysteine were decreased to a normal range and the clinical symptoms were significantly improved. After 3 months of treatment, the patient returned to school. He is now living with normal school life. In summary, children with late-onset MTHFR deficiency and secondary cerebral folate deficiency may lead to schizophrenia. This rare condition can be early diagnosed through analyses of blood and urine total homocysteine, amino acids in blood and folate in blood and cerebral fluid and successfully treated with folinic acid, vitamin B₆, vitamin B₁₂ and betaine.