背景:导致钠依赖性多维生素转运体(SMVT)缺陷的SLC5A6中的双等位基因致病变体最近被描述为一种维生素反应性先天代谢错误,模仿生物糖苷酶缺乏症。据我们所知,到目前为止,只有16名患者被报道患有各种临床表型,如神经病变和其他神经障碍,胃肠道功能障碍和未能茁壮成长,骨质减少,免疫缺陷,代谢性酸中毒,低血糖,和最近严重的心脏症状。
方法:我们描述了一个5个月大的女孩在感染性疾病过程中出现两次代谢失代偿和大量心力衰竭的反复发作的病例报告。我们比较临床,生物,从Pubmed数据库收集的先前文献(关键词:钠依赖性多维生素转运蛋白(SMVT),SMVT缺陷/紊乱/缺乏,SLC5A6基因/突变)。
结果:我们强调了这种疾病危及生命的表现,精神运动发育的停滞,严重和持续的低丙种球蛋白血症,此外,早期补充维生素(生物素每天15毫克,泛酸每天100毫克)的成功临床反应。代谢评估显示尿3-羟基异戊酸(3-HIA)的持续增加,如文献中先前报道的这种疾病。
结论:SMVT缺乏是一种维生素反应性先天代谢错误,可导致多种症状。尿3-羟基异戊酸的排泄增加和分离可能提示,在没有显著降低的生物素酶活性的情况下,SMVT缺乏。在等待SLC5A6测序结果的同时,应立即补充高剂量的生物素和泛酸,因为这种情况可能危及生命。
BACKGROUND: Biallelic pathogenic variants in SLC5A6 resulting in sodium-dependent multivitamin transporter (SMVT) defect have recently been described as a vitamin-responsive inborn error of metabolism mimicking biotinidase deficiency. To our knowledge, only 16 patients have been reported so far with various clinical phenotypes such as neuropathy and other neurologic impairments, gastro-intestinal dysfunction and failure to thrive, osteopenia, immunodeficiency, metabolic acidosis, hypoglycemia, and recently severe cardiac symptoms.
METHODS: We describe a case report of a 5-month-old girl presenting two recurrent episodes of metabolic decompensation and massive cardiac failure in the course of an infectious disease. We compare clinical, biological, and genetic findings of this patient to previous literature collected from Pubmed database (keywords: Sodium-dependent multivitamin transporter (SMVT), SMVT defect/disorder/deficiency, SLC5A6 gene/mutation).
RESULTS: We highlight the life-threatening presentation of this disease, the stagnation of psychomotor development, the severe and persistent hypogammaglobulinemia, and additionally, the successful clinical response on early vitamin supplementation (biotin 15 mg a day and pantothenic acid 100 mg a day). Metabolic assessment showed a persistent increase of urinary 3-hydroxyisovaleric acid (3-HIA) as previously reported in this disease in literature.
CONCLUSIONS: SMVT deficiency is a vitamin-responsive inborn error of metabolism that can lead to a wide range of symptoms. Increased and isolated excretion of urinary 3-hydroxyisovaleric acid may suggest, in the absence of markedly reduced biotinidase activity, a SMVT deficiency. Prompt supplementation with high doses of biotin and pantothenic acid should be initiated while awaiting results of SLC5A6 sequencing as this condition may be life-threatening.