Prenatal diagnosis of Smith-Lemli-Opitz syndrome, type II

Duplication of The SOX3 Gene in an Sry-negative 46,XX Male with Associated Congenital Anomalies of Kidneys and the Urinary Tract: Case Report and Review of the Literature

Disorders of sex development (DSD) are a group of rare conditions characterized by discrepancy between chromosomal sex, gonads and external genitalia. Congenital abnormalities of the kidney and urinary tract are often associated with DSD, mostly in multiple malformation syndromes. We describe the case of an 11-year-old Caucasian boy, with right kidney hypoplasia and hypospadias. Genome-wide copy number variation (CNV) analysis revealed a unique duplication of about 550 kb on chromosome Xq27, and a 46,XX karyotype, consistent with a sex reversal phenotype. This region includes multiple genes, and, among these, SOX3 emerged as the main phenotypic driver. This is the fifth case reporting a genomic imbalance involving the SOX3 gene in a 46,XX SRY-negative male, and the first with associated renal malformations. Our data provide plausible links between SOX3 gene dosage and kidney malformations. It is noteworthy that the current and reported SOX3 gene duplications are below the detection threshold of standard karyotypes and were found only by analyzing CNVs using DNA microarrays. Therefore, all 46,XX SRY-negative males should be screened for SOX3 gene duplications with DNA microarrays.

Primary disorders of metabolism and disturbed fetal brain development

There exists a link between the in utero metabolic environment and the development of the fetal nervous system. Prenatal neurosonography offers a unique, noninvasive tool in the detection of developmental brain malformations and the ability to monitor changes over time. This article explores the association of malformations of cerebral development reported in association with inborn errors of metabolism, and speculates on potential mechanisms by which such malformations arise. The detection of cerebral malformations prenatally should lead to a search for both genetic etiologies and inborn errors of metabolism in the fetus. Improving the changes of an early diagnosis provides for timely therapeutic interventions and it is hoped a brighter future for affected children and their families.

Smith-Lemli-Opitz syndrome: a variable clinical and biochemical phenotype

We have reviewed all known UK cases of Smith-Lemli-Opitz syndrome. Among 49 cases with proven 7-dehydrocholesterol reductase deficiency, half had been terminated or had died in infancy. The minimum incidence is 1 in 60,000. The frequent occurrence of hypospadias may account for 71% of recognised cases being male. Important common features which emerged include short thumbs, severe photosensitivity, aggressive behaviour, and atrioventricular septal defect. The typical facial appearance becomes less obvious with age and 20% of cases did not have 2/3 toe syndactyly. Biochemical measurements of serum 7-dehydrocholesterol did not correlate with clinical severity.

RSH (Smith-Lemli-Opitz) syndrome: "severe" phenotype with ectrodactyly

We describe the antenatal ultrasound findings of growth retardation, oligohydramnios, mesomelic limb shortness, and cardiac, renal, and hand defects in a fetus who was postnatally diagnosed as having RSH ("Smith-Lemli-Opitz") syndrome. An unusual finding was ectrodactyly of both hands.

Risk perception after CF carrier testing and impact of the test result on reproductive decision making

A correct interpretation of the result of a CF carrier test and a correct understanding of the risk of having a CF child is complicated by the limited sensitivity of the DNA test. The present paper addresses this problem, with special attention for the residual risk after a negative test result. Secondly, the impact of the test results on child bearing decisions is evaluated. Seventy percent of a sample of 200 subjects tested in the Center for Human Genetics in Leuven answered a mailed questionnaire and participated in an interview. Knowledge about the recessive transmission of CF was weak. In the case of both partners receiving a negative test result, more than half the subjects were not aware of the restrictions of DNA testing, and were convinced that there was no residual risk. Two thirds of the subjects from the 'carrier + negative test result couples' were aware of the residual risk of having a CF child. This risk did not hamper further reproduction. Carriers who were single or whose partner was not tested, had much difficulties to understand the risk. Although most of them had no idea about their exact risk level, it influenced their childbearing decisions to some extent. It was also shown that the own risk of having a CF child had an impact on attitudes toward reproduction in hypothetical situations with different risk levels.

First-trimester diagnosis of Smith-Lemli-Opitz syndrome

We report here the prenatal diagnosis of Smith-Lemli-Opitz (SLO) syndrome in the first trimester by direct measurement of 7-dehydrocholesterol (7-DHC) in a chorionic villus (CV) biopsy. The proband was diagnosed clinically at birth and the diagnosis was confirmed biochemically by demonstrating elevated 7-DHC in plasma. The family pursued prenatal diagnosis in their fourth, fifth, and sixth pregnancies. The fourth pregnancy spontaneously miscarried at 9 weeks' gestation. Analysis in both direct and cultured curetting tissue (identified as similar to CV tissue) showed an abnormal tissue neutral sterol pattern with an elevated 7-DHC concentration. The fifth pregnancy also miscarried spontaneously at 9 weeks but no tissue of unequivocal fetal origin could be identified to allow biochemical investigation. In the sixth pregnancy, ultrasound examination at the time of CV sampling showed a thickened nuchal fold. Direct analysis of the CV sample revealed elevated levels of 7-DHC consistent with the diagnosis of SLO. The pregnancy was terminated and both fetal tissue and cultured fetal cells showed marked increases in 7-DHC, confirming the prenatal diagnosis.

Pitfalls in measuring plasma cholesterol in the Smith–Lemli–Opitz syndrome

Correct quantitative results for plasma cholesterol, 7-dehydrocholesterol (7-DHC), and 8-dehydrocholesterol (8-DHC) are invaluable for making the correct diagnosis in patients with the Smith–Lemli–Opitz syndrome (SLO) and for biochemical monitoring of these patients during therapy. The enzymatic method for cholesterol measurement based on cholesterol oxidase gives falsely high values for plasma cholesterol in samples from patients with SLO. Both 7-DHC and 8-DHC contribute substantially to the test result, given that they are accepted substrates of cholesterol oxidase. All cholesterol methods making use of this enzyme are expected to give unreliable results with plasma samples from SLO patients. Cholesterol values found with these methods may be low-normal in individual cases with SLO. Therefore, other techniques for measuring cholesterol, 7-DHC, and 8-DHC, e.g., gas chromatography, should be used for diagnosing these patients and for follow-up during therapy. However, a normal value for plasma cholesterol, as obtained by gas chromatography, does not exclude SLO. The diagnosis should always be confirmed or excluded by testing for the presence of high concentrations of 7-DHC and 8-DHC in plasma. We found that one patient with a severe form of the disease had a plasma cholesterol concentration of 20 μmol/L—to our knowledge, the lowest value ever recorded in a human being.

Smith-Lemli-Opitz syndrome: prenatal diagnosis by quantification of cholesterol precursors in amniotic fluid

Until recently, the diagnosis of Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive malformation/mental retardation syndrome, was made on the basis of clinical criteria alone. As a result, prenatal diagnosis has been possible only if sonography disclosed distinct fetal malformations in a subsequent pregnancy. However, the recent description of increased levels of 7-dehydrocholesterol (cholesta-5,7-dien-3 beta-ol) in patients with SLOS, most likely caused by a deficiency of 3 beta-hydroxysteroid-delta 7-reductase, has provided an apparently reliable biochemical marker for diagnosis of SLOS. To determine if this abnormality of sterol metabolism has utility for prenatal diagnosis of SLOS, we measured the levels of neutral sterols in stored amniotic fluid samples from two SLOS pregnancies. In both cases, the diagnosis of SLOS was made in the neonatal period by clinical criteria and the finding of markedly increased levels of 7-dehydrocholesterol in plasma. Quantitative analysis by gas chromatography of sterols extracted from the amniotic fluid of both pregnancies revealed similar, markedly increased levels of 7-dehydrocholesterol and its precursor, lathosterol (cholest-7-en-3 beta-ol), both of which were undetectable in reference amniotic fluids. These findings suggest that abnormalities of cholesterol biosynthesis in SLOS may be sufficiently expressed in fetal life to permit prenatal diagnosis of this disorder by measurement of 7-dehydrocholesterol in amniotic fluid.

Unusual case of Smith-Lemli-Opitz syndrome "type II"

We describe a fetus with abnormalities suggestive, but not typical, of severe Smith-Lemli-Opitz syndrome (SLO). Biochemical studies demonstrated that there was a defect of cholesterol biosynthesis similar to that recently discovered in children with SLO. The findings in this fetus extend even further the wide spectrum of abnormalities of the SLO phenotype, and emphasize that a genetic pathological examination and biochemical studies should always be undertaken on atypical cases, especially fetuses.

Prenatal detection of the cholesterol biosynthetic defect in the Smith-Lemli-Opitz syndrome by the analysis of amniotic fluid sterols

The Smith-Lemli-Opitz (SLO or RSH) syndrome is an autosomal recessive disorder characterized by a recognizable pattern of minor facial anomalies, congenital anomalies of many organs, failure to thrive, and mental retardation. Its cause is a defect in cholesterol biosynthesis characterized by abnormally low plasma cholesterol levels and concentrations of the cholesterol precursor 7-dehydrocholesterol (7DHC) elevated up to several thousand-fold above normal. We used capillary column gas-chromatography to quantify sterols in amniotic fluid, amniotic cells, plasma, placenta, and breast milk from a heterozygous mother who had previously given birth to an affected son and in cord blood and plasma from her affected newborn daughter. The cholesterol concentration in amniotic fluid at 16 weeks gestation was normal, but 7DHC, normally undetectable, was greatly elevated. In cultured amniocytes, the level of 7DHC was 11% of total cholesterol, similar to cultured fibroblasts from patients with SLO syndrome. At 38 weeks, a girl with phenotype consistent with the syndrome was born. Cholesterol concentrations were abnormally low in cord blood and in the baby's plasma at 12 weeks, while levels of 7DHC were grossly elevated, confirming the prenatal diagnosis. The mother's plasma cholesterol increased steadily during gestation but remained below the lower 95% limit reported for normal control women. We conclude that it is now possible to detect the SLO syndrome at 16 weeks gestation by analyzing amniotic fluid sterols.

Prenatal diagnosis of Smith-Lemli-Opitz syndrome

An abnormality in cholesterol synthesis was described recently in the Smith-Lemli-Opitz (SLO) syndrome. Here we describe how the application of this finding has enabled an accurate prenatal diagnosis. We also discuss the possible use of this test in detecting heterozygotes.