Spondylocostal dysplasia and neural tube defects.

Spondylocostal dysplasia (Jarcho-Levin syndrome) comprises multiple malformations of the vertebrae and ribs coupled with a characteristic clinical picture of short neck, scoliosis, short trunk, and deformity of the rib cage. We describe a patient with the syndrome who also had spina bifida and diastematomyelia. We surmise that this association is not coincidental. Additional evidence is needed to support the hypothesis that spondylocostal dysplasia and neural tube defects are aetiologically related.     

Non-multifactorial neural tube defects

Although most neural tube defects (anencephaly, spina bifida) occur as isolated malformations, a substantial proportion are attributable to chromosome anomalies, known teratogens, or component manifestations of multiple anomaly syndromes. This review describes known chromosome alterations and the candidate genes residing in the altered region, as well as syndromes associated with neural tube defects and causative genes, if known.     

Analysis of methionine synthase reductase polymorphisms for neural tube defects risk association

Methionine synthase reductase (MTRR) regenerates methylated cobalamin levels from the oxidised cob(II)alamin form and in so doing plays a crucial role in maintaining the active state of methionine synthase (MTR). MTR is an essential enzyme catalyzing the conversion of homocysteine to methionine. Single nucleotide polymorphisms (SNPs) within the MTRR gene may potentially compromise MTR activity leading to elevated homocysteine levels, a known risk factor for neural tube defects (NTDs). We studied the MTRR polymorphisms I22M (66A-->G), S175L (524C-->T), and K350R (1049A-->G) as potential NTD risk factors in a large homogeneous Irish NTD population. Degree of risk was assessed via case/control comparison, log-linear analysis, and transmission disequilibrium testing. No association was found between NTDs and I22M in mothers (p = 0.16, OR1.14 [0.95-1.38], n = 447) or cases (p = 0.13, OR1.15 [0.96-1.38], n = 470) compared to controls (n = 476). A dominant I22M paternal effect was found through case/control comparison and log-linear modelling (p = 0.019) (goodness-of-fit p=0.91, OR 1.46 [1.10-1.93], n = 423). No significant NTD association was found with S175L or K350R in cases or their parents and no interactions were observed between these polymorphisms and the D919G variant of MTR or the A222V variant of 5,10-methylenetetrahydrofolate reductase (MTHFR). We also compared the frequencies of I22M, S175L, and K350R in African-Americans versus American-Caucasians. The frequencies of I22M and K350R differed significantly between the two groups (p = 0.0005 and p = 0.0001, respectively). Our findings do not support an important role for these MTRR variants in NTDs.     

Prior abortions and neural tube defects

Out of a series of 219 women who had had a child with anencephaly or spina bifida (ASB) in the Manchester area, there were 69 where this ASB pregnancy had been both preceded and succeeded by at least one other pregnancy. There was a significant excess of spontaneous abortions when the preceding pregnancy was compared with the succeeding pregnancy. Half of these preceding abortions were followed by curettage of the uterus, a fact which is a little against the trophoblastic rest hypothesis.     

Epidemiology of neural tube defects

The epidemiological investigation of the common open neural tube defects (NTDs), anencephaly, and spina bifida, has a long history. The most significant finding from these past studies of NTDs was the identification of the protective effect of maternal, periconceptional supplementation with folic acid. Fortuitously, the association between folic acid and NTDs became widely accepted in the early 1990s, at a time when genetic association studies of complex traits were becoming increasingly feasible. The confluence of these events has had a major impact on the direction of epidemiological, NTD research. Association studies to evaluate genes that may influence the risk of NTDs through their role in folate-related processes, or through other metabolic or developmental pathways are now commonplace. Moreover, the study of genetic as well as non-genetic, factors that may influence NTD risk through effects on the nutrient status of the mother or embryo has emerged as a major research focus. Research efforts over the past decade indicate that gene-gene, gene-environment, and higher-order interactions, as well as maternal genetic effects influence NTD risk, highlighting the complexity of the factors that underlie these conditions. The challenge for the future is to design studies that address these complexities, and are adequately powered to detect the factors or combination of factors that influence the development of NTDs.     

Trisomy 13 syndrome and neural tube defects

Abnormalities of the CNS, such as arhinencephaly or holoprosencephaly, are common findings in trisomy 13 syndrome. However, neural tube defects (NTDs) are rarely reported. A review of 267 patients in the literature on reported CNS developmental defects in trisomy 13 syndrome showed only 6 patients with lumbosacral NTDs. No case of encephalocele or anencephaly was found. We report on 3 patients with spina bifida from the records of 34 necropsies of karyotyped trisomy 13 syndrome, which were found among 403,710 births.     

神经管畸形的预防

NTDs为多因素疾病,发病率高,危害严重.现有的预防措施主要有围孕期服用叶酸制剂及产前监测.孕前筛查利用基因诊断筛查出生育NTDs的亲代高危人群,为孕前重点干预及孕期重点监测提供依据.若3种方法结合可使NTDs的预防措施更具针对性,从而最大限度地有效降低NTDs的发生率.