Female external genitalia and müllerian duct derivatives in a 46,XY infant with the smith-lemli-Opitz syndrome

Assessing Postnatal Mortality in Smith-Lemli-Opitz Syndrome

Smith-Lemli-Opitz syndrome (SLOS) is a rare autosomal recessive disorder caused by pathological variants in DHCR7, resulting in a deficiency in the enzyme 7-dehydrocholesterol reductase. This results in elevated levels of cholesterol precursors and typically low cholesterol levels, leading to a range of physical and cognitive challenges. Mortality rates in infants with severe SLOS are high, due to congenital malformations. Premature death has been described in individuals with SLOS, particularly in severely affected individuals. Further research is needed to understand postnatal mortality risk factors for individuals with SLOS. Understanding these factors could improve monitoring and prevention efforts. To investigate this, we obtained death certificates from the National Death Index (NDI) database on a cohort of individuals with SLOS who were enrolled in natural history studies at the National Institutes of Health Clinical Center (NCT00001721 and NCT05047354). Analysis and comparison of this deceased cohort showed that although premature death occurs in SLOS, many individuals with SLOS survive into adulthood. We also observed the risk of postnatal mortality increasing with higher severity scores and lower initial cholesterol levels. Trial Registration: NCT00001721 and NCT05047354.

A Case of Conservative Management of Intra-abdominal Polyorchidism in a Child

Polyorchidism is defined as the presence of 2 or more testes on the same side. A 7-year-old boy (46 XY) with multiple congenital abnormalities and nonpalpable bilateral gonads is presented. He underwent diagnostic laparoscopic surgery at 8 months old which revealed duplicated right testes and contralateral presence of persistent left Mullerian duct structures. A successful Fowler-Stephens orchidopexy in 2 stages was performed on both testicles. Postoperative ultrasonography showed orthotopic right testes of 0.15 and 0.28 cc. We propose testicular preservation in these patients to prevent early anorchia.

Statins for Smith-Lemli-Opitz syndrome

BACKGROUND

Smith-Lemli-Opitz syndrome (SLOS) is a multiple congenital malformations syndrome caused by defective cholesterol biosynthesis. Affected individuals show cholesterol deficiency and accumulation of various precursor molecules, mainly 7-dehydrocholesterol and 8-dehydrocholesterol. There is currently no cure for SLOS, with cholesterol supplementation being primarily a biochemical therapy of limited evidence. However, several anecdotal reports and preclinical studies have highlighted statins as a potential therapy for SLOS.

OBJECTIVES

To evaluate the effects of statins, either alone or in combination with other non-statin therapies (e.g. cholesterol, bile acid, or vitamin co-supplementation), compared to cholesterol supplementation alone or in combination with other non-statin therapies (e.g. bile acid or vitamin supplementation) on several important outcomes including overall survival, neurobehavioral features, and adverse effects in individuals with SLOS.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, five other databases and three trials registers on 15 February 2022, together with reference checking, citation searching and contact with study authors to identify additional studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) and quasi-RCTs with parallel or cross-over designs, and non-randomized studies of interventions (NRSIs) including non-randomized trials, cohort studies, and controlled before-and-after studies, were eligible for inclusion in this review if they met our prespecified inclusion criteria, i.e. involved human participants with biochemically or genetically diagnosed SLOS receiving statin therapy or cholesterol supplementation, or both.

DATA COLLECTION AND ANALYSIS

Two authors screened titles and abstracts and subsequently full-texts for all potentially-relevant references. Both authors independently extracted relevant data from included studies and assessed the risks of bias. We analyzed the data extracted from the included NRSIs and cohort studies separately from the data extracted from the single included RCT. We used a random-effects model to account for the inherent heterogeneity and methodological variation between these different study designs. We used GRADE to assess the certainty of evidence.

MAIN RESULTS

We included six studies (61 participants with SLOS); one RCT (N = 18), three prospective NRSIs (N = 20), and two retrospective NRSIs (N = 22). Five studies included only children, and two limited their participant inclusion by disease severity. Overall, there were nearly twice as many males as females. All six studies compared add-on statin therapy to cholesterol supplementation alone. However, the dosages, formulations, and durations of treatment were highly variable across studies. We judged the RCT as having a high risk of bias due to missing data and selective reporting. All included NRSIs had a serious or critical overall risk of bias assessed by the Risk Of Bias In Non-randomized Studies of Interventions tool (ROBINS-I). None of the included studies evaluated survival or reported quality of life (QoL). Only the included RCT formally assessed changes in the neurobehavioral manifestations of SLOS, and we are uncertain whether statin therapy improves this outcome (very low-certainty evidence). We are also uncertain whether the adverse events reported in the RCT were statin-related (very low-certainty evidence). In contrast, the adverse events reported in the NRSIs seem to be possibly due to statin therapy (risk ratio 13.00, 95% confidence interval 1.85 to 91.49; P = 0.01; low-certainty evidence), with only one of the NRSIs retrospectively mentioning changes in the irritability of two of their participants. We are uncertain whether statins affect growth based on the RCT or NRSI results (very low-certainty evidence). The RCT showed that statins may make little or no difference to plasma biomarker levels (low-certainty evidence), while we are uncertain of their effects on such parameters in the NRSIs (very low-certainty evidence).

AUTHORS' CONCLUSIONS

Currently, there is no evidence on the potential effects of statin therapy in people with SLOS regarding survival or QoL, and very limited evidence on the effects on neurobehavioral manifestations. Likewise, current evidence is insufficient and of very low certainty regarding the effects of statins on growth parameters in children with SLOS and plasma or cerebrospinal fluid (CSF) levels of various disease biomarkers. Despite these limitations, current evidence seemingly suggests that statins may increase the risk of adverse reactions in individuals with SLOS receiving statins compared to those who are not. Given the insufficient evidence on potential benefits of statins in individuals with SLOS, and their potential for causing adverse reactions, anyone considering this therapy should take these findings into consideration. Future studies should address the highlighted gaps in evidence on the use of statins in individuals with SLOS by collecting prospective data on survival and performing serial standardized assessments of neurobehavioral features, QoL, anthropometric measures, and plasma and CSF biomarker levels after statin introduction. Future studies should also attempt to use consistent dosages, formulations and durations of cholesterol and statin therapy.

Statins for Smith-Lemli-Opitz syndrome

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: 1. To evaluate the efficacy of statin therapy in reducing the frequency or severity of the neurobehavioral abnormalities seen in people with SLOS (e.g. aggression, anxiety, irritability, self-mutilation, autistic behaviors, sleep disturbances, etc.) (Wassif 2017). 2. To evaluate the potential effects of statin therapy on survival.

The Smith-Lemli-Opitz syndrome and dentofacial anomalies diagnostic: Case reports and literature review

OBJECTIVE

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder. It is due to a deficiency of 7-dehydrocholesterol reductase (DHCR7) that catalyses the reduction of 7-dehydrocholesterol (7-DHC) to cholesterol. The aim of this review is to gather all information, concerning diagnostic characteristics of this syndrome, with an emphasis on intraoral symptom presentation.

MATERIALS AND METHODS

We conducted a review of the literature, including articles between 1964 and 2017. Data was collected regarding the clinical diagnosis, pathophysiology and treatment of SLOS patients. Moreover, two clinical cases are described, illustrating the oral and facial anomalies of SLOS patients, at the regional university hospital of Lille, France.

DISCUSSION

Low cholesterol levels provoke a broad spectrum of clinical presentations, from mild to lethal forms. They can cause mental retardation, growth deficiency and congenital malformations. The SLOS features are often present at birth. Moreover, all the patients have facial anomalies. The dento-maxillofacial symptoms consist of crowded teeth, widely spaced incisors, oligodontia, polydontia, premature tooth eruption, enamel hypoplasia, a bifid uvula, broad alveolar ridges, bifid tongue, and Pierre-Robin syndrome symptoms (glossoptosis, retrognathia and cleft palate). These symptoms are warning signs and should increase the awareness of clinicians.

CONCLUSIONS

All healthcare professionals can contribute to the SLOS patient diagnostics. The dento-maxillofacial anomalies, illustrated by two case reports, could help to detect undiagnosed patients. An early detection might improve the outcome of these patients, as cholesterol supplementation can improve symptoms. This study can benefit orthodontists by enabling them to recognize the clinical signs of SLOS in order to refer these young patients to a specialist if the diagnosis has not been established.

Smith-Lemli-Opitz syndrome: clinical and biochemical correlates

BACKGROUND

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder caused by mutations in the DHCR7 gene that result in reduced cholesterol biosynthesis. The aim of the study was to examine the biochemical and clinical features of SLOS in the context of the emerging evidence of the importance of cholesterol in morphogenesis and steroidogenesis.

METHODS

We retrospectively reviewed the records of 18 patients (including four fetuses) with confirmed SLOS and documented their clinical and biochemical features.

RESULTS

Seven patients had branchial arch abnormalities, including micrognathia, immune dysfunction and hypocalcemia. Thymic abnormalities were found in three fetuses. All four patients with a cholesterol level of ≤0.35 mmol/L died. They all had electrolyte abnormalities (hyperkalemia, hyponatremia, hypocalcemia), necrotizing enterocolitis, sepsis-like episodes and midline defects including the branchial and cardiac defects. Patients with cholesterol levels ≥1.7 mmol/L had milder features and were diagnosed at 9 months to 25 years of age. All 10 patients had intellectual disability. One patient was found to have a novel mutation, c.1220A>G (p.Asn407Ser).

CONCLUSIONS

We suggest that screening for adrenal insufficiency and for hypoparathyroidism, hypothyroidism and immunodeficiency, should be done routinely in infants diagnosed early with SLOS. Early diagnosis and intervention to correct these biochemical consequences may decrease mortality and improve long-term outcome in these patients.

Spontaneously regressing brain lesions in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is a metabolic disorder caused by an inborn error of cholesterol synthesis that affects the development of many organ systems. Malformations in the central nervous system typically involve midline structures and reflect abnormal growth and differentiation of neurons and supporting cells. Despite these defects in central nervous system development, brain tumor formation has only rarely been reported in association with SLOS. We present three individuals with SLOS and lesions in the basal ganglia or brainstem detected by MRI that were concerning for tumor formation. However, the individuals' clinical and neurological course remained stable, and the lesions regressed after several years. These lesions have similarities to spongiotic changes observed in individuals with neurofibromatosis type 1 (NF1). Notably, impaired activity of small GTPases is present in both SLOS and NF1, perhaps giving mechanistic insight into the formation of these lesions.

Pathogenesis, Epidemiology, Diagnosis and Clinical Aspects of Smith-Lemli-Opitz Syndrome

INTRODUCTION

Smith-Lemli-Opitz Syndrome (SLOS) is a malformation syndrome inherited in an autosomal recessive fashion. It is due to a metabolic defect in the conversion of 7-dehydrocholesterol to cholesterol, which leads to an accumulation of 7-dehydrocholesterol and frequently a deficiency of cholesterol. The syndrome is characterized by typical dysmorphic facial features, multiple malformations, and intellectual disability.

AREAS COVERED

In this paper we provide an overview of the clinical phenotype and discuss how the manifestations of the syndrome vary depending on the age of the patients. We then explore the underlying biochemical defect and pathophysiological alterations that may contribute to the many disease manifestations. Subsequently we explore the epidemiology and succinctly discuss population genetics as they relate to SLOS. The next section presents the diagnostic possibilities. Thereafter, the treatment and management as is standard of care are presented.

EXPERT OPINION

Even though the knowledge of the underlying molecular mutations and the biochemical alterations is being rapidly accumulated, there is currently no efficacious therapy addressing neurological dysfunction. We discuss the difficulty of treating this disorder, which manifests as a combination of a malformation syndrome and an inborn error of metabolism. A very important factor in developing new therapies is the need to rigorously establish efficacy in controlled trials.

Brain magnetic resonance imaging findings in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is a neurodevelopmental disorder caused by inborn errors of cholesterol metabolism resulting from mutations in 7-dehydrocholesterol reductase (DHCR7). There are only a few studies describing the brain imaging findings in SLOS. This study examines the prevalence of magnetic resonance imaging (MRI) abnormalities in the largest cohort of patients with SLOS to date. Fifty-five individuals with SLOS (27 M, 28 F) between age 0.17 years and 25.4 years (mean = 6.2, SD = 5.8) received a total of 173 brain MRI scans (mean = 3.1 per subject) on a 1.5T GE scanner between September 1998 and December 2003, or on a 3T Philips scanner between October 2010 and September 2012; all exams were performed at the Clinical Center of the National Institutes of Health. We performed a retrospective review of these imaging studies for both major and minor brain anomalies. Aberrant MRI findings were observed in 53 of 55 (96%) SLOS patients, with abnormalities of the septum pellucidum the most frequent (42/55, 76%) finding. Abnormalities of the corpus callosum were found in 38 of 55 (69%) patients. Other findings included cerebral atrophy, cerebellar atrophy, colpocephaly, white matter lesions, arachnoid cysts, Dandy-Walker variant, and type I Chiari malformation. Significant correlations were observed when comparing MRI findings with sterol levels and somatic malformations. Individuals with SLOS commonly have anomalies involving the midline and para-midline structures of the brain. Further studies are required to examine the relationship between structural brain abnormalities and neurodevelopmental disability in SLOS.

Corpus callosum measurements correlate with developmental delay in Smith-Lemli-Opitz syndrome

BACKGROUND

Smith-Lemli-Opitz syndrome (SLOS) is a multiple malformation, neurodevelopmental disorder of cholesterol metabolism caused by mutations in 7-dehydrocholesterol reductase. Corpus callosum (CC) malformations and developmental delay are common, but the relation between the two has not been evaluated. This study hypothesizes shorter callosal length and smaller area correlate with higher serum 7-dehydrocholesterol and increased severity of neurodevelopmental delay in SLOS.

METHODS

Thirty-six individuals with SLOS (18M/18F) between 0.20 and 12.5 years (mean = 3.9, SD = 3.6) and 36 typically developing controls (18 boys and 18 girls) between 0.12 and 12.8 years (mean = 4.0, SD = 3.6) were each imaged once on a 1.5T scanner. One midsagittal image per study was selected for manual CC measurement. Gross motor, fine motor, and language developmental quotients; anatomical severity score; and serum sterol levels were assessed.

RESULTS

Shorter CC length and smaller area correlated with a lower developmental quotient in gross motor and language domains. Furthermore, length and area negatively correlated with a serum sterol precursors and severity score, and positively correlated with total cholesterol. Degree of developmental delay ranged from mild to severe, involving all domains.

CONCLUSIONS

For individuals with SLOS, smaller callosal area and length are associated with higher 7-dehydrocholesterol, severity scores, and developmental delay. The relationship between callosal development and biochemical abnormalities in this cohort may lead to further studies supporting imaging biomarkers.

Assays of plasma dehydrocholesteryl esters and oxysterols from Smith-Lemli-Opitz syndrome patients

Smith-Lemli-Opitz syndrome (SLOS) is caused by mutations in the gene encoding 3β-hydroxysterol-Δ(7)-reductase and as a result of this defect, 7-dehydrocholesterol (7-DHC) and 8-dehydrocholesterol (8-DHC) accumulate in the fluids and tissues of patients with this syndrome. Both 7- and 8-DHC are susceptible to peroxidation reactions, and several biologically active DHC oxysterols are found in cell and animal models of SLOS. Ex vivo oxidation of DHCs can be a confounding factor in the analysis of these sterols and their esters, and we developed HPLC/MS methods that permit the direct analysis of cholesterol, 7-DHC, 8-DHC, and their esters in human plasma, thus avoiding ex vivo oxidation. In addition, three oxysterols were classified as endogenously formed products by the use of an isotopically-labeled 7-DHC (d(7)-7-DHC) added to the sample before workup, followed by MS analysis of products formed. Analysis of 17 SLOS plasma samples shows that 8-DHC linoleate correlates better with the SLOS severity score of the patients than other sterols or metabolites, including cholesterol and 7-DHC. Levels of 7-ketocholesterol also correlate with the SLOS severity score. 8-DHC esters should have utility as surrogate markers of severity in SLOS for prognostication and as endpoints in clinical trials.

Smith-Lemli-Opitz syndrome: phenotype, natural history, and epidemiology

Smith-Lemli-Opitz syndrome (SLOS) is a congenital multiple anomaly/intellectual disability syndrome caused by a deficiency of cholesterol synthesis resulting from a deficiency of 7-dehydrocholesterol (7DHC) reductase encoded by DHCR7. SLOS is inherited in an autosomal recessive pattern. It is characterized by prenatal and postnatal growth retardation, microcephaly, a variable degree of intellectual disability that encompasses normal intelligence to severe intellectual deficiency, and multiple major and minor malformations. External malformations include distinctive facial features, cleft palate, postaxial polydactyly, 2-3 syndactyly of the toes, and underdeveloped external genitalia in males, while internal anomalies may affect every organ system. The clinical spectrum is wide, and rare individuals have been described with normal development and only minor malformations. The clinical diagnosis of SLOS is confirmed by demonstrating an abnormally elevated concentration of the cholesterol precursor, 7DHC, in serum or other tissues, or by the presence of two DHCR7 mutations. The enzymatic deficiency results in decreased cholesterol and increased 7DHC levels, both during embryonic development and after birth. The malformations found in SLOS may result from decreased cholesterol, increased 7DHC or a combination of these two factors. This review discusses the physical and behavioral phenotype of SLOS, the diagnostic approaches, the natural history from the prenatal period to adulthood, and current understanding of the pathophysiology of SLOS.

Mutational spectrum of Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS; OMIM #270400) is an autosomal recessive malformation syndrome characterized by a large spectrum of morphogenic and congenital anomalies. SLOS is caused by mutations in the DHCR7 gene, which encodes 7-dehydrocholesterol reductase, the enzyme that catalyzes the final step in cholesterol biosynthesis. We report on 154 currently known mutations in DHCR7 identified in patients affected with SLOS and discuss their coding consequences. These 154 mutations include 130 missense, 8 nonsense, 8 deletions, 2 insertions, 1 indel, and 5 splice site mutations. Using information available from published case reports and from patients identified in our clinical diagnostic laboratory, we analyzed correlations between genotype, clinical presentation and 7-dehydrocholesterol level.

Adrenal function in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is a multiple malformation syndrome due to mutations of the 7-dehydrocholesterol reductase gene (DHCR7), which leads to a deficiency of cholesterol synthesis and an accumulation of 7-dehydrocholesterol. The SLOS clinical spectrum ranges from multiple major malformations to a mild phenotype with minor anomalies and intellectual disability. Several children with SLOS and adrenal insufficiency have been described. We performed ovine corticotropin (oCRH) testing in 35 SLOS patients and 16 age- and gender-matched controls. We reviewed prior adrenocorticotropin (ACTH) stimulation tests of our SLOS patients (19 of 35 available) and reviewed results of ACTH stimulation tests from 10 additional SLOS patients. Results from oCRH testing showed that patients with SLOS had significantly higher ACTH baseline values than healthy controls (24.8 ± 15.3 pg/ml vs. 17.8 ± 7.5 pg/ml, P = 0.034). However, no statistically significant differences were noted for peak ACTH values (74.4 ± 35.0 pg/ml vs. 64.0 ± 24.9 pg/ml, P = 0.303) and for baseline (14.2 ± 7.8 mcg/dl vs. 14.2 ± 6.3 mcg/dl, P = 0.992) and peak cortisol values (28.2 ± 7.9 mcg/dl vs. 24.8 ± 8.1 mcg/dl, P = 0.156). The area-under-the-curve (AUC) was not significantly different in SLOS patients compared to controls for both ACTH (250.1 ± 118.7 pg/ml vs. 195.3 ± 96.6 pg/ml, P = 0.121) as well as cortisol secretion (83.1 ± 26.1 mcg/dl vs. 77.8 ± 25.9 mcg/dl, P = 0.499). ACTH stimulation test results were normal in 28 of 29 tests. The individual with the abnormal test results had subsequent normal oCRH tests. The slightly increased baseline ACTH level seen during oCRH testing may be due to compensated adrenocortical insufficiency. However, we were able to show that our patients with SLOS had an adequate glucocorticoid response, and thus, in mild to moderate cases of SLOS stress steroid coverage may not be warranted.

Discordant phenotype and sterol biochemistry in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is a malformation syndrome resulting from mutations of the 7-dehydrocholesterol reductase (DHCR7) gene. During cholesterol biosynthesis, DHCR7 catalyzes the conversion of 7-dehydrocholesterol (7DHC) to cholesterol. A clinical diagnosis of SLOS is confirmed biochemically by the presence of elevated levels of 7DHC. Phenotypic severity of SLOS has previously been shown to correlate with the 7DHC/cholesterol ratio. We describe a patient with a severe SLOS phenotype, but a very low serum 7DHC/cholesterol ratio. We show that this discordance is due to alternative splicing of a previously unreported IVS5+3 A>T mutation. This mutation results in the transcription of both normal and mutant mRNA transcripts. We postulate that alternative splicing of the IVS5+3 A>T results in insufficient DHCR7 activity during embryogenesis, but sufficient DHCR7 activity once cholesterol synthetic rates decrease postnatally. This unique case underscores the adjunctive use of fibroblast and molecular testing in ambiguous cases of SLOS and may provide insight into the potential efficacy of therapeutic interventions altering postnatal cholesterol biosynthesis.

Malformation syndromes caused by disorders of cholesterol synthesis

Cholesterol homeostasis is critical for normal growth and development. In addition to being a major membrane lipid, cholesterol has multiple biological functions. These roles include being a precursor molecule for the synthesis of steroid hormones, neuroactive steroids, oxysterols, and bile acids. Cholesterol is also essential for the proper maturation and signaling of hedgehog proteins, and thus cholesterol is critical for embryonic development. After birth, most tissues can obtain cholesterol from either endogenous synthesis or exogenous dietary sources, but prior to birth, the human fetal tissues are dependent on endogenous synthesis. Due to the blood-brain barrier, brain tissue cannot utilize dietary or peripherally produced cholesterol. Generally, inborn errors of cholesterol synthesis lead to both a deficiency of cholesterol and increased levels of potentially bioactive or toxic precursor sterols. Over the past couple of decades, a number of human malformation syndromes have been shown to be due to inborn errors of cholesterol synthesis. Herein, we will review clinical and basic science aspects of Smith-Lemli-Opitz syndrome, desmosterolosis, lathosterolosis, HEM dysplasia, X-linked dominant chondrodysplasia punctata, Congenital Hemidysplasia with Ichthyosiform erythroderma and Limb Defects Syndrome, sterol-C-4 methyloxidase-like deficiency, and Antley-Bixler syndrome.

Effects of dietary cholesterol and simvastatin on cholesterol synthesis in Smith-Lemli-Opitz syndrome

Deficient cholesterol and/or excessive 7-dehydrocholesterol (7-DHC) may be responsible for the pathology of Smith-Lemli-Opitz syndrome (SLOS). Both high-cholesterol diets given to ameliorate cholesterol deficiency while decreasing 7-DHC and cholesterol-enriched diets plus simvastatin to further decrease sterol synthesis have been used as potential therapies. However, the effect of dietary cholesterol and simvastatin on cholesterol synthesis in SLOS has not been reported. Twelve subjects with SLOS enrolled in the study: Nine had received a high cholesterol diet (HI) for 3 y and three were studied after 4 wk on a low cholesterol diet (LO). Cholesterol fractional synthesis rate (FSR) was measured after oral administration of deuterium oxide, using gas chromatography isotope ratio mass spectrometry. FSR was lower in HI compared with LO (HI: 1.46 +/- 0.62%/d; LO: 4.77 +/- 0.95%/d; p < 0.001). Three HI subjects were retested after 0.8 y taking simvastatin (HI + ST). Simvastatin tended to reduce FSR and significantly decreased (p < 0.01) plasma 7-DHC compared with cholesterol supplementation alone. The study demonstrates the utility of the deuterium incorporation method to understand the effect of therapeutic interventions in SLOS. The data suggest that dietary cholesterol supplementation reduces cholesterol synthesis in SLOS and further support the rationale for the combined treatment of SLOS with a cholesterol-enriched diet and simvastatin.

Mild Smith-Lemli-Opitz syndrome: further delineation of 5 Polish cases and review of the literature

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder caused by reduced activity of 7-dehydrocholesterol reductase, resulting in an increased concentrations of 7-dehydrocholesterol and 8-dehydrocholesterol in body fluids and tissues. Phenotypically it is characterized by wide range of abnormalities, from mild to lethal forms what causes difficulties in its clinical diagnostics. To further delineate the physical spectrum of the mild form of Smith-Lemli-Opitz syndrome, especially with regard to genotype-phenotype correlation, we describe 5 Polish patients with mild phenotype (one with novel mutation in DHCR7 gene and four published before) and analyze 18 other cases from the literature. As the conclusion we give recommendation for tests toward SLOS in cases with "idiopathic" intellectual impairment and/or behavioral anomalies, as well as in biochemically doubtful but clinically fitting cases with overall gestalt and history of this syndrome.

Residual cholesterol synthesis and simvastatin induction of cholesterol synthesis in Smith-Lemli-Opitz syndrome fibroblasts

Smith-Lemli-Opitz syndrome (RSH/SLOS) is an autosomal recessive, malformation syndrome caused by mutations in the 3beta-hydroxysterol delta7-reductase gene (DHCR7). DHCR7 catalyzes the reduction of 7-dehydrocholesterol (7DHC) to cholesterol. We report the mutation analysis and determination of residual cholesterol synthesis in 47 SLOS patients, and the effects of treatment of SLOS skin fibroblasts with simvastatin. Using deuterium labeling we have quantified the amount of synthesized cholesterol and 7DHC in homozygote, heterozygote, and control fibroblast cell lines. In SLOS fibroblasts, the fraction of synthesized cholesterol to total sterol synthesis ranged from undetectable to over 50%. This establishes that different mutant alleles encode enzymes with varying degrees of residual activity. There was a correlation between increased phenotypic severity and decreased residual cholesterol synthesis (r(2)=0.45, p<0.0001). Simvastatin treatment of SLOS fibroblasts with residual DHCR7 enzymatic activity decreased 7DHC levels and increased cholesterol synthesis. This increase in cholesterol synthesis is due to increased expression of a mutant allele with residual function. Determination of residual enzymatic activity for specific DHCR7 mutant alleles will help in understanding the processes underlying the broad phenotypic spectrum found in this disorder and will be useful in identifying patients who may benefit from simvastatin therapy.

Characterization of liver involvement in defects of cholesterol biosynthesis: long-term follow-up and review

Inborn defects of cholesterol biosynthesis are a group of metabolic disorders presenting with mental retardation and multiple congenital anomalies (MCA/MR syndromes). Functional and structural liver involvement has been reported as a rare (2.5-6%) complication of the Smith-Lemli-Opitz syndrome (SLOS) and it has not been fully characterized. Here, we report on a long-term follow-up study of four patients with SLOS, and one case with lathosterolosis who presented with liver disease and underwent an extensive diagnostic work-up. Reports of liver involvement in cholesterol biosynthesis defects are reviewed. Two main different patterns of liver involvement emerged: progressive cholestasis, and stable isolated hypertransaminasemia. In our series, the first pattern was found in two patients with SLOS and one with lathosterolosis, and the second in two SLOS cases. Cholestasis was associated with early lethality and normal serum gamma-glutamyl-transferase (GGT) levels in SLOS, while possible prolonged survival and high GGT levels were seen in lathosterolosis. Hepatic fibrosis was present in both conditions. Liver biopsy performed in one of our SLOS patients with isolated hypertransaminasemia, showed only mild hydropic degeneration of the hepatocytes. The presence of liver involvement in 16% of the SLOS patients diagnosed at our Center suggests that this complication might have been underestimated in previously reported cases, possibly overshadowed by the severity of multiple malformations. Fetal hepatopathy, cholestasis, and isolated hypertransaminasemia can occur also in other disorders of cholesterol biosynthesis, such as mevalonic aciduria, desmosterolosis, Conradi-Hunermann syndrome, Greenberg dysplasia, and Pelger-Huet homozygosity syndrome. This group of inherited disorders should be considered in the differential diagnosis of patients presenting with liver disease associated with developmental delay and/or multiple malformations. Periodic liver function evaluations are recommended in these patients.

Lowered DHCR7 activity measured by ergosterol conversion in multiple cell types in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder of cholesterol metabolism characterized by multiple congenital anomalies and mental retardation. SLOS results from mutations in 7-dehydrocholesterol Delta7 reductase (DHCR7), the gene encoding the final enzyme involved in cholesterol biosynthesis. The resulting cholesterol deficiency and excessive 7- and 8-dehydrocholesterol (7-DHC, 8-DHC) in plasma and tissues are almost always diagnostic for SLOS. We measured DHCR7 activity in fibroblasts, amniocytes, and chorionic villi from controls, heterozygotes, and SLOS subjects. The enzyme activity (expressed as percent conversion of substrate) was significantly lower in untransformed fibroblasts from SLOS subjects (4.47%+/-0.72) compared to untransformed fibroblasts from heterozygotes (26.6%+/-4.6, p<0.01) or controls (50.6%+/-5.3, p<0.001). We also measured plasma cholesterol and 7-DHC, determined the severity score and identified DHCR7 mutations for most of the subjects. There was no significant correlation of enzyme activity with severity score, plasma cholesterol level, plasma 7-DHC level, or the 7-DHC:cholesterol ratio. We conclude that even though enzyme activity as measured by the ergosterol assay may not correlate with severity, this assay has the potential to distinguish SLOS cells from carrier or unaffected cells in a variety of cell types, and should prove useful in confirming a diagnosis in atypical cases where sterol levels are equivocal. Additionally, it may be important to measure residual enzyme activity in SLOS subjects being considered for a trial of statins, as this treatment could theoretically be detrimental in subjects with little or no DHCR7 activity. Finally, the data suggest a threshold enzyme activity of 8% conversion, below which disease occurs.

Identification of three patients with a very mild form of Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive malformation syndrome characterized by mental retardation, congenital anomalies, and growth deficiency. The syndrome is caused by a block in cholesterol biosynthesis at the level of 7-dehydrocholesterol reductase (7-DHCR), which results in elevated levels of the cholesterol precursor 7-dehydrocholesterol (7-DHC) and its isomer 8-dehydrocholesterol (8-DHC). We report on three patients from two families with a very mild clinical presentation of SLOS. Their plasma cholesterol values were normal and their plasma levels of 7- and 8- DHC were only slightly elevated. In cultured skin fibroblasts, a significant residual 7-DHCR activity was found. All three patients were compound heterozygotes for a novel mutation affecting translation initiation (M1L). Two of them had the common IVS8-1G>C null mutation and the third patient an E448K mutation in the 7-DHCR gene. Our findings emphasize the importance of using a sensitive method for measuring precursors of cholesterol in combination with mutation analysis to analyze patients with only minimal clinical SLOS-like signs.

Biochemical abnormality associated with Smith-Lemli-Opitz syndrome in an infant with features of Rutledge multiple congenital anomaly syndrome confirms that the latter is a variant of the former

We describe a female infant with morphologic features of Rutledge multiple-congenital-anomaly syndrome (RMCAS) and biochemical features of Smith-Lemli-Opitz syndrome (SLOS). She had microcephaly with hypoplastic cerebral frontal lobes and cerebellum, agenesis of the splenium of corpus callosum, abnormal facies including hypertelorism with bilateral inner epicanthal folds, a broad nasal bridge with slightly anteverted nares and patent choanae, low set ears and complex conchal formation, high-arched palate and thick maxillary alveolar ridges, and micrognathia. Her chest was broad, genitalia were ambiguous, and uterus was bicornuate. Skeletal abnormalities included a hypoplastic appendicular skeleton, post-axial hexadactyly of the right hand and the left foot, syndactyly of bilateral 2nd-3rd toes and left 5th-6th toes, right talipes varus and left talipes valgus, and fused L5-S1 vertebrae. Congenital heart disease consisted of hypoplastic left heart, coronary sinus agenesis, ostium secundum and ostium primum defects, and a thickened septum primum. The lungs were hypolobated and the kidneys manifested oligopapillary hypoplasia. Total colonic Hirschsprung disease was noted microscopically. Analysis of liver tissue taken at postmortem examination revealed the ratio of 7-dehydrocholesterol and cholesterol to be 143 (expected, 0.28 +/- 0.28). Although initially described as a distinct syndrome, RMCAS was merged with the severe form of SLOS, because of significantly overlapping features [Online Mendelian Inheritance in Man (OMIM) #268670]. The biochemical data showing an excess of 7-dehydrocholesterol and low cholesterol in the liver tissue of our case supports this viewpoint.

Insuficiência Adrenal Primária de Causa Genética

A insuficiência adrenal primária pode resultar em uma situação de risco de vida, quando não tratada ou quando o paciente é submetido a situações de estresse. Desta maneira, o reconhecimento, diagnóstico e tratamento correto e precoce da insuficiência adrenal é de fundamental importância na prática clínica. Por outro lado, o avanço no conhecimento dos mecanismos moleculares das diferentes causas genéticas de insuficiência adrenal tem permitido melhor entendimento não só da fisiopatologia, mas também do desenvolvimento e fisiologia da glândula adrenal. Esta revisão apresenta aspectos clínicos e moleculares de diferentes causas de insuficiência adrenal de origem genética.

Inborn errors of sterol biosynthesis

The known disorders of cholesterol biosynthesis have expanded rapidly since the discovery that Smith-Lemli-Opitz syndrome is caused by a deficiency of 7-dehydrocholesterol. Each of the six now recognized sterol disorders-mevalonic aciduria, Smith-Lemli-Opitz syndrome, desmosterolosis, Conradi-Hünermann syndrome, CHILD syndrome, and Greenberg dysplasia-has added to our knowledge of the relationship between cholesterol metabolism and embryogenesis. One of the most important lessons learned from the study of these disorders is that abnormal cholesterol metabolism impairs the function of the hedgehog class of embryonic signaling proteins, which help execute the vertebrate body plan during the earliest weeks of gestation. The study of the enzymes and genes in these several syndromes has also expanded and better delineated an important class of enzymes and proteins with diverse structural functions and metabolic actions that include sterol biosynthesis, nuclear transcriptional signaling, regulation of meiosis, and even behavioral modulation.

Genetic disorders of cholesterol biosynthesis in mice and humans

Over the past few years, the number of identified inborn errors of cholesterol biosynthesis has increased significantly. The first inborn error of cholesterol biosynthesis to be characterized, in the mid 1980s, was mevalonic aciduria. In 1993, Irons et al. ( 1 ) (M. Irons, E. R. Elias, G. Salen, G. S. Tint, and A. K. Batta, Lancet 341:1414, 1993) reported that Smith-Lemli-Opitz syndrome, a classic autosomal recessive malformation syndrome, was due to an inborn error of cholesterol biosynthesis. This was the first inborn error of postsqualene cholesterol biosynthesis to be identified, and subsequently additional inborn errors of postsqualene cholesterol biosynthesis have been characterized to various extent. To date, eight inborn errors of cholesterol metabolism have been described in human patients or in mutant mice. The enzymatic steps impaired in these inborn errors of metabolism include mevolonate kinase (mevalonic aciduria as well as hyperimmunoglobulinemia D and periodic fever syndrome), squalene synthase (Ss-/- mouse), 3beta-hydroxysteroid Delta14-reductase (hydrops-ectopic calcification-moth-eaten skeletal dysplasia), 3beta-hydroxysteroid dehydrogenase (CHILD syndrome, bare patches mouse, and striated mouse), 3beta-hydroxysteroid Delta8,Delta7-isomerase (X-linked dominant chondrodysplasia punctata type 2, CHILD syndrome, and tattered mouse), 3beta-hydroxysteroid Delta24-reductase (desmosterolosis) and 3beta-hydroxysteroid Delta7-reductase (RSH/Smith-Lemli-Opitz syndrome and Dhcr7-/- mouse). Identification of the genetic and biochemical defects which give rise to these syndromes has provided the first step in understanding the pathophysiological processes which underlie these malformation syndromes.

Incidence of Smith-Lemli-Opitz syndrome in Ontario, Canada

Smith-Lemli-Opitz syndrome (OMIM 270400) (SLOS) is caused by inherited enzymatic deficiency of 3beta-hydroxysterol-Delta7-reductase (7-dehydrocholesterol-Delta7-reductase, DHCR7). SLOS is diagnosed clinically by the demonstration of elevated levels of 7-dehydrocholesterol (7DHC) in body fluids or tissues. SLOS is associated with mental retardation of variable degree and severe behavior abnormalities. The physical abnormalities range from minor facial anomalies to lethal malformations of the central nervous system, heart, kidneys, and other organs. The exact incidence of SLOS is not known. Although there exist estimates of the incidence of SLOS ranging from 1 in 20,000 to 1 in 60,000, no prospective studies of the incidence of SLOS, based on the clinical data and biochemical diagnosis of SLOS, have been performed. Five unrelated cases of SLOS were diagnosed in Ontario during a 12-month period. The diagnoses were made based on the demonstration of elevated 7DHC in plasma or amniotic fluid. The birth rate for Ontario for that period was 132,000 births. The incidence of SLOS in Ontario was at least 1 in 26,500 pregnancies in 1999-2000. Given that 86% of the population of Ontario is of European origin, the incidence of SLOS in the Ontario population of European origin was at least 1 in 22,700. As infants with mild forms of SLOS born during this period may remain undiagnosed, these numbers likely are underestimates. This observation has implications for prenatal and newborn screening for this potentially treatable inherited disorder.

The Smith-Lemli-Opitz syndrome: a novel metabolic way of understanding developmental biology, embryogenesis, and dysmorphology

The brief history of the Smith-Lemli-Opitz syndrome (SLOS) (MIM 270400) reflects that of latter 20th century dysmorphology and biochemical and molecular genetics: from its first description as a rare but characteristic multiple malformation syndrome known only to a handful of dysmorphologists, to a relatively common Garrodian defect with a complex molecular basis that has captured the attention of researchers and basic scientists from the fields as diverse as embryology, developmental biology, sterol biochemistry, epidemiology, and teratology. The discovery of the underlying biochemical defect - deficiency of 3beta-hydroxysteroid-Delta7-reductase (DHCR7), an enzyme catalyzing the last step of cholesterol biosynthesis, and the resultant generalized cholesterol deficiency - has led to an explosion of knowledge of this biochemical pathway and to a paradigm shift in the recognition of metabolic deficiencies as causes of dysmorphic syndromes. Characterization of the human DHCR7 gene and the identification of mutations in patients with SLOS have revealed a complex picture of molecular heterogeneity and provided insights into the structure and function of DHCR7. SLOS is the first metabolic malformation syndrome with profound effects on the body plan, and its discovery has paved the way to the discovery of a number of other defects of the cholesterol synthetic pathway.

RSH/Smith-Lemli-Opitz syndrome: a multiple congenital anomaly/mental retardation syndrome due to an inborn error of cholesterol biosynthesis

The RSH/Smith-Lemli-Opitz syndrome (RSH/SLOS) is an autosomal recessive multiple congenital anomaly/mental retardation syndrome caused by an inborn error of cholesterol biosynthesis. The RSH/SLOS phenotypic spectrum is broad; however, typical features include microcephaly, ptosis, a small upturned nose, micrognathia, postaxial polydactaly, second and third toe syndactaly, genital anomalies, growth failure, and mental retardation. RSH/SLOS is due to a deficiency of the 3beta-hydroxysterol Delta(7)-reductase, which catalyzes the reduction of 7-dehydrocholesterol (7-DHC) to cholesterol. This inborn error of cholesterol biosynthesis results in elevated serum and tissue 7-DHC levels. The 3beta-hydroxysterol Delta(7)-reductase gene (DHCR7) maps to chromosome 11q12-13, and to date 66 different mutations of this gene have been identified in RSH/SLOS patients. Identification of the biochemical basis of RSH/SLOS has led to development of therapeutic regimens based on dietary cholesterol supplementation and has increased our understanding of the role cholesterol plays during embryonic development.

The Smith-Lemli-Opitz syndrome

The Smith-Lemli-Opitz syndrome (SLOS) is one of the archetypical multiple congenital malformation syndromes. The recent discovery of the biochemical cause of SLOS and the subsequent redefinition of SLOS as an inborn error of cholesterol metabolism have led to important new treatment possibilities for affected patients. Moreover, the recent recognition of the important role of cholesterol in vertebrate embryogenesis, especially with regard to the hedgehog embryonic signalling pathway and its effects on the expression of homeobox genes, has provided an explanation for the abnormal morphogenesis in the syndrome. The well known role of cholesterol in the formation of steroid hormones has also provided a possible explanation for the abnormal behavioural characteristics of SLOS.

Biochemical variants of Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz (SLO or RSH) syndrome is characterized by multiple congenital anomalies, mental retardation, and defective growth; it results from an inherited defect in the biosynthesis of cholesterol. Patients have elevated plasma concentrations of 7-dehydrocholesterol, the immediate biosynthetic precursor of cholesterol and most also have low circulating levels of cholesterol. To understand better the biochemical basis of clinical variability, we evaluated cholesterol biosynthesis in lymphoblasts from 3 unrelated SLOS patients with distinct phenotypes. One patient has "type I SLOS", the second has the more severe "type II SLOS" and the third is classified as atypical and had been postulated to have a defect in sterol transport. The lymphoblasts of each patient show normal subcellular localization of cholesterol and 7-dehydrocholesterol by gradient fractionation. Biochemical differences in the ability of the lymphoblasts to convert 7-dehydrocholesterol to cholesterol are described and correspond to the severity of disease (type II > type I > atypical). Recently, the gene responsible for most SLOS cases (DHCR7) was mapped to chromosome 11 and mutations in DHCR7 were found in each of these patients. The biochemical differences described here likely result from the different mutations observed in DHCR7.

RSH (so-called Smith-Lemli-Opitz) syndrome

Now known as a Garrodian inborn error caused by the homozygous state of many different autosomal recessive mutations of the 7-dehydrocholesterol reductase gene leading to deficient conversion of 7-dehydrocholesterol to cholesterol, the RSH (so-called Smith-Lemli-Opitz) syndrome has become a paradigmatic metabolic malformation syndrome in a pathway that also involves cause and pathogenesis of desmosterolosis, two forms of the Conradi-Hünermann-Happle type chondodysplasia punctata and its mouse homologs, and the Greenberg "moth-eaten" skeletal dysplasia and the CHILD syndrome. Many other defects in this pathway remain to be discovered.

Prenatal diagnosis of Smith-Lemli-Opitz syndrome in a pregnancy with low maternal serum oestriol and a sex-reversed fetus

A cytogenetically normal male fetus was subsequently found to have female external genitalia, a cardiac malformation and mid-trimester intra-uterine growth retardation by ultrasound examination. The maternal serum oestriol level was low. The combination of low oestriol and sonographic findings suggested Smith Lemli Opitz syndrome (SLO), which was confirmed by a markedly increased amniotic fluid level of 7-dehydrocholesterol. We review the differential diagnosis of apparent sex reversal in a fetus and low maternal serum oestriol level. To further examine the specificity of low maternal oestriol level as a marker for SLO a follow-up study of 12141 pregnancies screened for Down syndrome using three biochemical markers: alpha-fetoprotein, beta-human chorionic gonadotrophin and oestriol was performed. 26 pregnancies had an oestriol level that was 0.25 MoM or less. SLO was not diagnosed clinically in any of the liveborn children ascertained through a low maternal oestriol level. Nine of the pregnancies ended in spontaneous miscarriage. Although the frequency of SLO in pregnancies with low maternal oestriol levels or sex-reversed fetuses is unknown, the diagnosis of SLO should, nevertheless, be considered in both clinical settings.

Smith-Lemli-Opitz syndrome: phenotypic extreme with minimal clinical findings

Smith-Lemli-Opitz syndrome (SLO) is caused by inherited enzymatic deficiency of 7-dehydrocholesterol-delta7-reductase and resultant cholesterol deficiency. It comprises a characteristic combination of facial features, malformations, and mental retardation. We report on three related patients (two brothers and their first cousin) with mental retardation and minimal physical signs in whom the diagnosis of SLO was delayed for a number of years. The presence of a third-degree relative in the absence of consanguinity in this family supports the proposed high population carrier frequency. Our report suggests that cases of mild SLO remain undiagnosed and untreated, and that awareness of this common cause of mental retardation is low.

Mutations in the human sterol delta7-reductase gene at 11q12-13 cause Smith-Lemli-Opitz syndrome

The Smith-Lemli-Opitz syndrome (SLOS; also known as "RSH syndrome" [MIM 270400]) is an autosomal recessive multiple malformation syndrome due to a defect in cholesterol biosynthesis. Children with SLOS have elevated serum 7-dehydrocholesterol (7-DHC) levels and typically have low serum cholesterol levels. On the basis of this biochemical abnormality, it has been proposed that mutations in the human sterol Delta7-reductase (7-DHC reductase; E.C.1.3.1.21) gene cause SLOS. However, one could also propose a defect in a gene that encodes a protein necessary for either the expression or normal function of sterol Delta7-reductase. We cloned cDNA encoding a human sterol Delta7-reductase (DHCR7) on the basis of its homology with the sterol Delta7-reductase from Arabidopsis thaliana, and we confirmed the enzymatic function of the human gene product by expression in SLOS fibroblasts. SLOS fibroblasts transfected with human sterol Delta7-reductase cDNA showed a significant reduction in 7-DHC levels, compared with those in SLOS fibroblasts transfected with the vector alone. Using radiation-hybrid mapping, we show that the DHCR7 gene is encoded at chromosome 11q12-13. To establish that defects in this gene cause SLOS, we sequenced cDNA clones from SLOS patients. In three unrelated patients we have identified four different mutant alleles. Our results demonstrate both that the cDNA that we have identified encodes the human sterol Delta7-reductase and that mutations in DHCR7 are responsible for at least some cases of SLOS.

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.

Regulation of sexual dimorphism in mammals

Sexual dimorphism in humans has been the subject of wonder for centuries. In 355 BC, Aristotle postulated that sexual dimorphism arose from differences in the heat of semen at the time of copulation. In his scheme, hot semen generated males, whereas cold semen made females (Jacquart, D., and C. Thomasset. Sexuality and Medicine in the Middle Ages, 1988). In medieval times, there was great controversy about the existence of a female pope, who may have in fact had an intersex phenotype (New, M. I., and E. S. Kitzinger. J. Clin. Endocrinol. Metab. 76: 3-13, 1993.). Recent years have seen a resurgence of interest in mechanisms controlling sexual differentiation in mammals. Sex differentiation relies on establishment of chromosomal sex at fertilization, followed by the differentiation of gonads, and ultimately the establishment of phenotypic sex in its final form at puberty. Each event in sex determination depends on the preceding event, and normally, chromosomal, gonadal, and somatic sex all agree. There are, however, instances where chromosomal, gonadal, or somatic sex do not agree, and sexual differentiation is ambiguous, with male and female characteristics combined in a single individual. In humans, well-characterized patients are 46, XY women who have the syndrome of pure gonadal dysgenesis, and a subset of true hermaphrodites are phenotypic men with a 46, XX karyotype. Analysis of such individuals has permitted identification of some of the molecules involved in sex determination, including SRY (sex-determining region Y gene), which is a Y chromosomal gene fulfilling the genetic and conceptual requirements of a testis-determining factor. The purpose of this review is to summarize the molecular basis for syndromes of sexual ambiguity seen in human patients and to identify areas where further research is needed. Understanding how sex-specific gene activity is orchestrated may provide insight into the molecular basis of other cell fate decisions during development which, in turn, may lead to an understanding of aberrant cell fate decisions made in patients with birth defects and during neoplastic change.

Correlation of severity and outcome with plasma sterol levels in variants of the Smith-Lemli-Opitz syndrome

OBJECTIVES

To determine whether type I and the more severe type II variant of Smith-Lemli-Opitz syndrome have the same metabolic defect and to learn which plasma sterol measurements best predict survival.

METHODS

Plasma sterols were measured in 33 individuals (24 type I, 9 type II) with a clinical diagnosis of the syndrome.

RESULTS

Cholesterol levels were abnormally low (61 +/- 34 mg/dl) in type I subjects, whereas concentrations of the cholesterol precursor 7-dehydrocholesterol and its isomer 8-dehydrocholesterol were elevated 40- to 10,000-fold. Plasma cholesterol levels were significantly lower and total dehydrocholesterol levels higher in type II than in type I. Six children with the type II variant died by 13 weeks with mean plasma cholesterol levels 6.2 +/- 3.1 mg/dl, versus 17 +/- 11 mg/dl in the three surviving children with type II (p < 0.05). No child with a cholesterol level 7 mg/dl or less lived longer than 13 weeks.

CONCLUSIONS

Patients with type I and type II variants of Smith-Lemli-Opitz syndrome have markedly reduced activity of the enzyme that converts 7-dehydrocholesterol to cholesterol, but the extent of the block is far more complete in type II. Survival correlates strongly with higher plasma cholesterol concentrations.

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.