Harold M. Nitowsky

An association between low maternal serum α-fetoprotein and fetal chromosomal abnormalities

Abstract An index case of “undetectable” maternal serum α-fetoprotein at 16 weeks in the first pregnancy of a 28-year-old woman was associated with birth of an infant with trisomy 18. This fortuitous finding stimulated a retrospective study of prenatally diagnosed chromosomal abnormalities. From among a series of 3,862 genetic amniocenteses, 32 cases of fetal autosomal trisomy were diagnosed for which corresponding maternal serum and amniotic fluid α-fetoprotein data could be retrieved. From a second laboratory, nine additional cases were added. The maternal serum α-fetoprotein levels expressed as multiples of the median were significantly lower in distribution for these 41 women than those from a group of normal matched control subjects (p

A new gene, EVC2, is mutated in Ellis-van Creveld syndrome

Ellis-van Creveld syndrome (EvC; MIM 225500) is an autosomal recessive chondrodysplastic dwarfism. Thus far, the identified mutations in the EVC gene located on chromosome 4p16 have only accounted for illness in a small proportion of affected individuals. In this report we describe a novel gene, EVC2, that is mutated in an Ashkenazi individual with EvC syndrome. Our findings demonstrate for the first time that the heterogeneity observed in this disorder is not solely the result of mutations in a single gene.

Methylenetetrahydrofolate reductase (MTHFR): The incidence of mutations C677T and A1298C in the Ashkenazi Jewish population

The polymorphic mutation C677T in the gene of MTHFR is considered a risk mutation for spina bifida and vascular disease. Another common mutation on the MTHFR gene, A1298C, has also been described as another risk mutation. We studied the frequencies of these two mutations on DNA samples from healthy Jewish individuals and compared them to the frequency of these mutations in DNA samples obtained from healthy individuals in South Texas. The presence of the C677T allele was determined by PCR and Hinf I digestion, and mutation A1298C by PCR and Mbo II digestion. A total of 310 alleles was examined for C677T in the Ashkenazi samples and 400 alleles in the non-Jewish samples. The rate of C677T among the Ashkenazi Jewish alleles was 47.7% as compared to 28.7% among the alleles from the non-Jewish population. The difference is statistically significant, P < 0.0005. Mutation A1298C was examined in 298 alleles of Jewish individuals and 374 alleles of non-Jewish counterparts from Texas. The rate of the A1298C mutation in the Jewish samples was 27.2% whereas in the non-Jewish was 35%. This was also statistically significant, P < 0.031. No individuals were homozygous for both mutations or were found to be homozygous for one mutation with heterozygosity of the other mutation, and that the C677T and the A1298C alleles did not occur in cis position. This study shows a unique distribution of C677T and the A1298C alleles among the Ashkenazi Jews. In spite of high frequency of C677T mutation, spina bifida is less common among Ashkenazi Jews. Further studies are needed to establish whether the C677T and the A1298C mutations have an impact on vascular disease in the Ashkenazi Jewish population.

The prenatal diagnosis of adrenoleukodystrophy. Demonstration of increased hexacosanoic acid levels in cultured amniocytes and fetal adrenal gland

Summary: Amniocentesis was performed in two women heterozygous for adrenoleukodystrophy (ALD). One fetus was male, and the hexacosanoic acid (C26) level in the cultured amniotic cells was 0.808 μg per mg of protein, compared to 0.104 ± 0.069 (S.D.) in controls. Pregnancy was interrupted at 22 wk gestation. The fetal adrenal cortex showed the ultrastructural inclusions characteristic of ALD and C26 accounted for 35% of the fatty acids in the cholesterol esters extracted from this tissue, more than one thousand times control. The second amniocentesis was performed in a woman who was also heterozygous for an electrophoretic variant of glucose 6-phosphate dehydrogenase (G6PD), and a member of a kindred showing genetic linkage of loci for ALD and G6PD. The fetus was female and the C26 level in cultured amniotic cells was 0.577. Pregnancy was interrupted at 11 wk for reasons unrelated to ALD. Study of C26 level and G6PD type in cultured fetal tissues confirmed heterozygosity for ALD.Speculation: The capacity to identify the adrenoleukodystrophy (ALD) hemizygote prenatally together with the availability of tests of plasma and/or cultured skin fibroblasts, which can identify most women heterozygote for this disorder, provide the opportunity for families at risk for ALD to have normal children. It is striking that the fetal adrenal was already abnormal, because clinical evidence of adrenal insufficiency would not have been expected until more than 4 years postnatally. Because the abnormal fatty acids are of dietary origin at least in part, it may be possible to diminish or prevent their accumulation by reducing their intake.

Human hexosaminidase isozymes: chromatographic separation as an aid to heterozygote identification.

The correct identification of Tay-Sachs heterozygotes requires a reliable procedure for separation and quantiation of the hexosaminidase isozymes. The most commonly employed method involves thermal inactivation of the heat labile hexosaminidase A assay of residual enzyme activity. This procedure, however, consistently yields a significantly lower absolute and relative activity of hexosaminidase A and a higher activity of the thermostable components (B and I) in comparison with the results obtained by DEAE-cellulose chromatography. DEAE-cellulose chromatographic separation of the hexosaminidase isozymes in serum following thermal inactivation reveals the presence of relative and absolute increase in the activity of the B and I components in addition to loss of the heat-labile A isozyme. Because the conversion of hexosaminidase A into thermostable forms by heating may vary according to the conditions employed, the thermal inactivation procedure may lead to ambiguity in heterozygote identification. This difficulty can be minimized by fractionation of the hexosaminidase isozymes by DEAE-cellulose chromatography followed by assay of the individual components. In addition to the Tay-Sachs carrier state, other conditions can alter the distribution of the hexosaminidase isozymes in tissues and body fluids. For example in serum of patients with juvenile diabetes mellitus there is a characteristic elevation of hexosaminidase B and less consistently, of hexosaminidase A. Since the activity of hexosaminidase A in serum of diabetics fractionated by ion exchange chromatography is at least as high as the activity in serum of healthy non-carriers, patients with diabetes can be easily differentiated from Tay-Sachs heterozygotes. Similarly, the distribution of the hexosaminidase isozymes in serum is altered during pregnancy, where there is usually a significant rise in hexosaminidase A and I (P). However, during pregnancy activities of hexosaminidase A and I in serum of obligate Tay-Sachs carriers are only 50% of the values observed in non-carriers at comparable gestational periods. Since the absolute activities of hexosaminidase A in serum of pregnant carriers obtained by ion exchange chromatography do not overlap with the activities in serum of non-carrier pregnant women at comparable gestational periods, this method has obvious advantages for identification of pregnancies where the fetus may be at risk for Tay-Sachs disease.

Altered Lysosomal Glycohydrolase Activities in Juvenile Diabetes Mellitus

Studies have been carried out on activities of lysosomal β-N-acetylhexosaminidase (hex), β-galactosidase (β-gal), α-glucosidase (α-glu), and acid phosphatase (AP) in serum and urine from patients with juvenile diabetes and matched controls. There is a large increase in blood and urinary hex activity (the former presenting three distinct patterns of abnormality), a moderate increase in urinary β-gal, and a small increase in urinary α-glu activity, but no elevation of blood or urinary AP in the diabetics. Urinary α-glu activity in the diabetics shows striking inhibition by glucose, and this may reflect a similar phenomenon in vivo. Although glycohydrolase activities are elevated in patients with no detectable microangiopathy, more striking changes may be observed in patients with severe small-vessel disease. These alterations may be associated with increased glycoprotein catabolism in the diabetic, an area in need of further studies in the human and experimental diabetic animal.

Procedure-related fetal losses in transplacental versus nontransplacental genetic amniocentesis

OBJECTIVE We hypothesize that loss rates after amniocentesis do not differ in transplacental and nontransplacental taps performed by experienced operators. STUDY DESIGN Subjects were 1000 women undergoing second-trimester amniocentesis: 745 were referred for maternal age; 132 for positive maternal serum alpha-fetoprotein screens, 41 indicating a risk for fetal neural tube defect, 91 indicating a risk for fetal chromosome abnormality; and 123 were referred for other reasons. All procedures were videotaped. The placenta was anterior in 518 cases; in 306 of these the needle went through the placenta. All pregnancies were prospectively evaluated through delivery. RESULTS There were 13 losses among the 1000 procedures (1.3%). The transplacental losses occurred from 4 to 71 days after procedure, median 26.5 days; the nontransplacental losses from 12 days after procedure to term, median 25 days. The loss rate was essentially similar in the two categories: six transplacental (1.96%) and seven nontransplacental (1%) (relative risk 1.52 [95% confidence limits 0.84 to 2.75], p = 0.23). If the three patients with elevated maternal serum alpha-fetoprotein values were excluded from data analysis, the loss rates in the two groups were virtually identical (relative risk 0.98 [95% confidence limits 0.38 to 2.54], p = 1.0000). CONCLUSION Transplacental amniocentesis does not appear to increase the fetal loss rate in the hands of experienced surgeons. Moreover, in view of the time span between amniocentesis and loss in both groups, a procedural cause seems questionable.

Palmar crease variants and their clinical significance: a study of newborns at risk.

Summary: An analysis of palmar crease variants was carried out in a group of “at risk” newborns, without any evident congenital anomalies. This group consisted of 108 prematures, 74 infants who were small for gestational age, 62 newborns with history of gestational complications, and 46 newborns with a history of intrauterine methadone exposure.A system of classification was developed based on observations of 500 normal newborns as control subjects, 466 normal mothers, and 200 normal children. The palmar crease variants can be divided into four main groups, schematically presented as normal variants, simian crease and its variants, Sydney line and its variants, and another group of unusual variants which do not fit into the other groups. A study of these groups revealed that familial components, race, sex, and age are factors that can influence the expression of palmar crease patterns. There is an increased frequency of abnormal creases in each of the groups of “at risk” newborns. Moreover, there is an apparent association of interrupted transverse creases and intrauterine methadone exposure.Speculation: Our findings suggest that examination of palmar creases and the demonstration of variant patterns may provide a useful, objective indicator of possible abnormal fetal development. Since it is important to utilize a standard scheme in routine newborn examination, both to identify palmar crease variants and to establish a baseline for comparative studies, a system for classification of palmar creases is presented.

Monozygotic twins discordant for sex.

A pair of monozygotic, adolescent twins is discordant for sex. The phenotypic female twin has chromosome constitution of 46, XY/45, X. She displays many signs of Turners syndrome, including typical facies, webbed neck, malformed left kidney, high plasma gonadotropins, and streak ovaries. However, her height is 154 cm which exceeds the height usually reported in Turners syndrome. The male twin has a karyotype of 46, XY and normal sexual development. Only two other reports of pairs of monozygotic twins of opposite sex have been published.

Incontinentia pigmenti in a newborn male infant with DNA confirmation

We report on a woman with incontinentia pigmenti (IP), who had two successive term pregnancies. The first pregnancy ended in the birth of a male infant, who is alive and well at 2 years. A second liveborn male had early postnatal distress and died after 1 day of life, after a fulminating clinical course. Polymorphic microsatellite markers, closely linked to the IP gene on the X chromosome, showed that each son inherited a different X chromosome from his mother. Although in most instances IP appears to be prenatally lethal for the male, the phenotype is not completely known. We propose that the neonatal phenotype may be characterized by lethal disturbances in the hematopoietic and immunologic systems.