Inborn Error Of Cholesterol Biosynthesis Research Articles

Síndrome dismórfico em recém-nascido com hipocolesterolemia

Introduction: There are various diseases caused by errors of the biosynthesis of cholesterol and Smith-Lemli-Opitz syndrome is the most frequent. Clinical Case: Infant admitted at 31 days of life with feeding difficulties since birth and failure to thrive. He presented dysmorphic craniofacial features and pos axial limb malformations, hypotonia, weak spontaneous movements and week reflexes. Investigation revealed hypocholesterolemia and an elevation of cholesterol precursors, which allowed the diagnosis of Smith-Lemli-Opitz syndrome, confirmed by molecular analysis. The administration of cholesterol resulted in weight gain. Discussion: The Smith-Lemli-Opitz syndrome is a multiple congenital malformation syndrome, of autosomal recessive transmission, resulting from an inborn error of cholesterol biosynthesis. It is caused by a defect in 7-dehydrocholesterol reductase, which decreases levels of cholesterol and elevates its precursors. Supplementation with cholesterol has been proven successful in the achievement of partial clinical improvements.

Radiographic features of the skeleton in disorders of post-squalene cholesterol biosynthesis.

Disorders of post-squalene cholesterol biosynthesis are inborn errors of metabolism characterised by multiple congenital abnormalities, including significant skeletal involvement. The most frequent and best-characterised example is the Smith-Lemli-Opitz syndrome. Nine other disorders are known, namely autosomal-recessive Antley-Bixler syndrome, Greenberg dysplasia, X-linked dominant chondrodysplasia punctata, X-linked recessive male emopamil-binding protein deficiency, CHILD syndrome, CK syndrome, sterol C4 methyloxidase-like deficiency, desmosterolosis and lathosterolosis. This study provides an overview of the radiologic features observed in these diseases. A common pattern of limb abnormalities is recognisable, including polydactyly, which is typically post-axial and rarely interdigital and can involve all four limbs, and syndactyly of the toes. Chondrodysplasia punctata is specifically associated with a subgroup of disorders of cholesterol biosynthesis (Greenberg dysplasia, CHILD syndrome, X-linked dominant chondrodysplasia punctata, male emopamil-binding protein deficiency). The possible occurrence of epiphyseal stippling in the Smith-Lemli-Opitz syndrome, initially reported, does not appear to be confirmed. Stippling is also associated with other congenital disorders such as chromosomal abnormalities, brachytelephalangic chondrodysplasia punctata (X-linked recessive chondrodysplasia punctata, disruptions of vitamin K metabolism, maternal autoimmune diseases), rhizomelic chondrodysplasia punctata (peroxisomal disorders) and lysosomal storage disorders. In the differential diagnosis of epiphyseal stippling, a moth-eaten appearance of bones, asymmetry, or presence of a common pattern of limb abnormalities indicate inborn errors of cholesterol biosynthesis. We highlight the specific differentiating radiologic features of disorders of post-squalene cholesterol biosynthesis.

Antioxidant Supplementation Ameliorates Molecular Deficits in Smith-Lemli-Opitz Syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an inborn error of cholesterol biosynthesis characterized by diminished cholesterol and increased 7-dehydrocholesterol (7-DHC) levels. 7-Dehydrocholesterol is highly reactive, giving rise to biologically active oxysterols. 7-DHC-derived oxysterols were measured in fibroblasts from SLOS patients and an in vivo SLOS rodent model using high-performance liquid chromatography tandem mass spectrometry. Expression of lipid biosynthesis genes was ascertained by quantitative polymerase chain reaction and Western blot. The effects of an antioxidant mixture of vitamin A, coenzyme Q10, vitamin C, and vitamin E were evaluated for their potential to reduce formation of 7-DHC oxysterols in fibroblast from SLOS patients. Finally, the effect of maternal feeding of vitamin E enriched diet was ascertained in the brain and liver of newborn SLOS mice. In cultured human SLOS fibroblasts, the antioxidant mixture led to decreased levels of the 7-DHC-derived oxysterol, 3β,5α-dihydroxycholest-7-en-6-one. Furthermore, gene expression changes in SLOS human fibroblasts were normalized with antioxidant treatment. The active ingredient appeared to be vitamin E, as even at low concentrations, it significantly decreased 3β,5α-dihydroxycholest-7-en-6-one levels. In addition, analyzing a mouse SLOS model revealed that feeding a vitamin E enriched diet to pregnant female mice led to a decrease in oxysterol formation in brain and liver tissues of the newborn Dhcr7-knockout pups. Considering the adverse effects of 7-DHC-derived oxysterols in neuronal and glial cultures and the positive effects of antioxidants in patient cell cultures and the transgenic mouse model, we believe that preventing formation of 7-DHC oxysterols is critical for countering the detrimental effects of DHCR7 mutations.

Living with inborn errors of cholesterol biosynthesis: lessons from adult patients

In the last decades, nine inherited errors of the distal part of cholesterol biosynthesis have been recognized. Affected patients present complex malformation syndromes involving different organs and systems with variable degrees of severity. We report on the phenotype evolution of three patients with enzymatic defects at three distinct steps of such pathway: Smith-Lemli-Opitz syndrome, X-linked dominant chondrodysplasia punctata type 2 and congenital hemidysplasia with ichthyosiform erythroderma and limb defects syndrome. The patients' natural history, from childhood to adulthood, is thoroughly described in order to contribute for a better knowledge of these diseases. Our ultimate goals are to contribute for a better characterization of the long-term course of these metabolic disorders and for the recognition of such diseases in older patients.

A routine method for cholesterol and 7-dehydrocholesterol analysis in dried blood spot by GC–FID to diagnose the Smith–Lemli–Opitz syndrome

This work was aimed to implement a fast and simple method to quantify cholesterol (CHOL) and 7-dehydrocholesterol (7-DHC) in dried blood spot (DBS) to diagnose the Smith–Lemli–Opitz syndrome (SLOS), an inborn error of CHOL biosynthesis. We developed and validated a GC–FID method for separation and quantification of underivatized CHOL and 7-DHC using a DBS disc of 6mm with a run time of 9min. Correlation coefficients (r) of calibration curves ranged from 0.998 to 0.999 for CHOL and from 0.997 to 0.998 for 7-DHC. Within-day and between-day imprecision (CV%), accuracy (%), carry-over, and extraction efficacy (%) were also evaluated for validation. CHOL and 7-DHC were analyzed in DBS and plasma samples from 8 SLOS patients and 30 unaffected subjects. In SLOS patients, 7-DHC/CHOL ratios in DBS and plasma samples ranged from 0.035 to 1.448 and from 0.012 to 0.926, respectively. Results from calibration curves, quality controls and patient samples reveal that the method is suitable to analyze DBS to screen patients affected by SLOS.

Mutations in the SC4MOL gene encoding a novel methyl sterol oxidase cause autosomal recessive psoriasisiform dermatitis, microcephaly and developmental delay

AbstractDisorders of cholesterol biosynthesis have clinical manifestations involving skeleton, eyes, neurologic development, and skin. We describe a patient with congenital cataracts, developmental delay, microcephaly, and low serum cholesterol who developed severe psoriasiform dermatitis and arthralgias beginning at age 3. Her brain MRI indicatedminor gliosis. Quantitative sterol analysis of patient plasma and skin showed marked elevation of 4alpha-methyl- and 4, 4'-dimethylsterols, indicating a deficiency in the first step of sterol C4 demethylation in cholesterol biosynthesis. Molecular studies showed mutations in SC4MOL, a gene predicted to encode a sterol C4 methyl oxidase. Thus, our patient has a previously undescribed inborn error of cholesterol biosynthesis. Cellular studies with patient-derived fibroblasts showed higher mitotic rate than control cells in cholesterol-depleted medium, in which de novo cholesterol biosynthesis was increased with the accumulation of methylsterol. Immunologic analyses showed dysregulation of immune-related receptors in the patient and her father. Inhibition of sterol C4 methyl oxidase in human transformed lymphoblasts or in fresh leukocytes induced activation of cell cycle, and immune receptor dysregulation. These findings suggest that methylsterols influence mitotic capacity and immune function. SC4MOL is situated within the psoriasis susceptibility locus PSORS9, and is likely a genetic risk factor for common psoriasis.

Functional analysis of cholesterol biosynthesis by RNA interference

Inborn errors of cholesterol biosynthesis caused by dysfunctionality of single enzymes are known to cause severe malformation syndromes like X-linked chondrodysplasia punctata (CDPX2), CHILD syndrome or Smith–Lemli–Opitz-syndrome (SLOS). In this study we established the method of RNA interference (RNAi) for analyzing the molecular mechanisms underlying disrupted cholesterol biosynthesis. For different genes involved in the cholesterol biosynthesis pathway-NAD(P) dependent steroid dehydrogenase-like (NSDHL), 17-beta hydroxysteroid dehydrogenase type 7 (HSD17B7) and emopamil binding protein (EBP)-shRNA sequences were designed and tested for their effectiveness. For a better comparability of the experiments and to avoid different transfection efficiencies, examined shRNA sequences which reached a knock down of at least 80% were stably transfected in a HeLa cell line with a tetracycline-regulated expression (HeLa T-REx). These stable transfected cell lines represent novel tools for the analysis of cholesterol biosynthesis.

Vitamin D status in patients affected by Smith‐Lemli‐Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an inborn error of cholesterol biosynthesis characterized by developmental delay and multiple malformations. Some of the patients have skin photosensitivity and therefore tend to avoid direct exposure to sunlight.SLOS patients typically have low concentrations of cholesterol and abnormally high concentrations of its precursor 7-dehydrocholesterol (7-DHC) in biological fluids and tissues. 7-DHC is also a precursor in the cutaneous synthesis of vitamin D. Sunlight exposure plays a major role in this pathway and reactions transforming 7-DHC into vitamin D and then into 25-hydroxyvitamin D are known not to be specifically regulated. The aim of this study was to evaluate vitamin D status in SLOS patients. We measured 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D serum concentrations and markers of calcium metabolism in five SLOS patients. Despite abnormally high concentrations of 7-DHC, circulating concentrations of vitamin D metabolites were not significantly different from appropriate controls matched for sex, age and season of blood collection. The analysis of historical serum samples stored in our laboratory from the same cases plus 10 other SLOS patients further supported these findings. Our data suggest that SLOS patients have a peculiar vitamin D metabolism that protects them from vitamin D intoxication. This appears to be due in most cases to decreased transformation of 7-DHC into 25-hydroxyvitamin D, perhaps depending on reduced sunlight exposure as a consequence of photosensitivity. Possible alternative mechanisms are discussed.

Retinal degeneration in a rodent model of Smith-Lemli-Opitz syndrome: electrophysiologic, biochemical, and morphologic features.

To assess the electrophysiologic, histologic, and biochemical features of an animal model of Smith-Lemli-Opitz syndrome (SLOS). Sprague-Dawley rats were treated with AY9944, a selective inhibitor of 3beta-hydroxysterol-Delta(7)-reductase (the affected enzyme in SLOS). Dark- and light-adapted electroretinograms were obtained from treated and control animals. From each animal, 1 retina was analyzed by microscopy, and the contralateral retina plus serum samples were analyzed for sterol composition. The main outcome measures were rod and cone electroretinographic amplitudes and implicit times, outer nuclear layer (ONL) thickness, rod outer segment length, pyknotic ONL nucleus counts, and the 7-dehydrocholesterol/cholesterol mole ratio in the retina and serum. By 10 weeks' postnatal age, rod and cone electroretinographic wave amplitudes in AY9944-treated animals were significantly reduced and implicit times were significantly increased relative to controls. Maximal rod photoresponse and gain values were reduced approximately 2-fold in treated animals relative to controls. The ONL thickness and average rod outer segment length were reduced by approximately 18% and 33%, respectively, and ONL pyknotic nucleus counts were approximately 4.5-fold greater in treated animals relative to controls. The retinal pigment epithelium of treated animals contained massive amounts of membranous/lipid inclusions not routinely observed in controls. The 7-dehydrocholesterol/cholesterol mole ratios in treated retinas and serum samples were approximately 5:1 and 9:1, respectively, whereas the ratios in control tissues were essentially zero. This rodent model exhibits the key biochemical hallmarks associated with SLOS and displays electrophysiologic deficits comparable to or greater than those observed in the human disease. Clinical Relevance These results predict retinal degeneration in patients with SLOS, particularly those with the more severe (type II) form of the disease, and may be more broadly relevant to other inborn errors of cholesterol biosynthesis. This animal model may also be of use in evaluating therapeutic treatments for SLOS and in understanding the slow phototransduction kinetics observed in patients with SLOS.

Molecular mechanisms underlying limb anomalies associated with cholesterol deficiency during gestation: implications of Hedgehog signaling.

Human disorders caused by inborn errors of cholesterol biosynthesis are characterized by dysmorphogenesis of multiple organs. This includes limb malformations that are observed at high frequency in some disorders, such as the Smith-Lemli-Opitz syndrome, indicating a pivotal role of cholesterol in limb morphogenesis. Recently, it has been demonstrated that cholesterol can modulate the activity of the Hedgehog proteins, that act as morphogens to regulate the precise patterning of many embryonic structures, among which the developing limbs. To provide insight in the functions of cholesterol during limb development and in the potential role of Hedgehog signaling in the genesis of limb defects, we developed an in vivo rat model of cholesterol deficiency. We show here that treatment with Triparanol, a distal inhibitor of cholesterol biosynthesis, induced patterning defects of the autopod at high frequency, including pre-axial syndactyly and post-axial polydactyly, thus reproducing limb anomalies frequently observed in humans. Using in situ hybridization, we show that these malformations originate from a modification of Sonic Hedgehog signaling in the limb bud at 13 days post-coitum, leading to a deficiency of the anterior part of the limb. This deficiency results in an imbalance of Indian Hedgehog expression in the forming cartilage, ultimately leading to reduced interdigital apoptosis and syndactyly. Our study thus unravels the molecular mechanisms underlying the genesis of limb defects associated with cholesterol deficiency in rodents, and most probably in humans.

Anesthesia and airway management of pediatric patients with Smith-Lemli-Opitz syndrome.

SMITH-LEMLI-OPITZ syndrome (SLOS) is an autosomal recessive disorder with an incidence of between 1 in 26,500 pregnancies in Canada and 1 in 50,000 pregnancies in the United States. The syndrome results from an inborn error of cholesterol biosynthesis involving a deficiency of 3β-hydroxysterol Δ 7 -reductase, the enzyme that catalyzes the reduction of 7-dehydrocholesterol to cholesterol. As a result, patients with SLOS have abnormal embryonic development, high plasma concentrations of 7-dehydrocholesterol, and usually decreased plasma concentrations of cholesterol. This biochemical defect is associated with a broad spectrum of clinical manifestations with potentially profound anesthetic implications. Patients with SLOS cans have severe growth failure, congenital anomalies affecting most organ systems, early death, developmental delay, and self-injurious and ritualistic behavior. Of special concern to anesthesiologists are the typical dysmorphic facial features, including micrognathia, cleft palate, and a small and abnormally hard tongue, which can present a challenge in airway management of patients with SLOS. The broad spectrum of congenital anomalies and potential increase in lifespan with dietary cholesterol replacement therapy make it very likely that diagnostic and therapeutic interventions requirign anesthesia will be needed in patients with SLOS. However, since the discovery of the biochemical defect in SLOS, little has been reported on the anesthetic management of these patients. In this report, we describe the administration of 20 anesthetics in 14 patients with confirmed biochemical diagnosis of SLOS. Our focus was on airway management, and because of previous reports of difficult intubations in some of our patients, we chose to use fiberoptic laryngoscopy as the initial technique to achieve tracheal intubation.

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), 3β-hydroxysteroid Δ14-reductase (hydrops-ectopic calcification-moth-eaten skeletal dysplasia), 3β-hydroxysteroid dehydrogenase (CHILD syndrome, bare patches mouse, and striated mouse), 3β-hydroxysteroid Δ8,Δ7-isomerase (X-linked dominant chondrodysplasia punctata type 2, CHILD syndrome, and tattered mouse), 3β-hydroxysteroid Δ24-reductase (desmosterolosis) and 3β-hydroxysteroid Δ7-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.

Biochemical, phenotypic and neurophysiological characterization of a genetic mouse model of RSH/Smith--Lemli--Opitz syndrome.

The RSH/Smith--Lemli--Opitz syndrome (RSH/SLOS) is a human autosomal recessive syndrome characterized by multiple malformations, a distinct behavioral phenotype with autistic features and mental retardation. RSH/SLOS is due to an inborn error of cholesterol biosynthesis caused by mutation of the 3 beta-hydroxysterol Delta(7)-reductase gene. To further our understanding of the developmental and neurological processes that underlie the pathophysiology of this disorder, we have developed a mouse model of RSH/SLOS by disruption of the 3 beta-hydroxysterol Delta(7)-reductase gene. Here we provide the biochemical, phenotypic and neurophysiological characterization of this genetic mouse model. As in human patients, the RSH/SLOS mouse has a marked reduction of serum and tissue cholesterol levels and a marked increase of serum and tissue 7-dehydrocholesterol levels. Phenotypic similarities between this mouse model and the human syndrome include intra-uterine growth retardation, variable craniofacial anomalies including cleft palate, poor feeding with an uncoordinated suck, hypotonia and decreased movement. Neurophysiological studies showed that although the response of frontal cortex neurons to the neurotransmitter gamma-amino-n-butyric acid was normal, the response of these same neurons to glutamate was significantly impaired. This finding provides insight into potential mechanisms underlying the neurological dysfunction seen in this human mental retardation syndrome and suggests that this mouse model will allow the testing of potential therapeutic interventions.

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 3β-hydroxysterol Δ7-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 3β-hydroxysterol Δ7-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.

Cholesterol supplementation enhances growth of phallus in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive inborn error of cholesterol biosynthesis due to a deficiency of the last enzyme of the cholesterol synthetic pathway, 7-dehydrocholesterol reductase. Affected patients have low concentrations of cholesterol and elevation of the cholesterol precursor, 7-dehydrocholesterol (7-DHC). Multiple congenital anomalies, dysmorphic facies, and growth and developmental retardation are common. Severely affected males have ambiguous genitalia. We believe that the genital anomalies seen in affected males are due to deficiency of androgens, but this has never been proven.The infant was diagnosed prenatally with SLOS by sterol analysis of amniotic fluid at 30 weeks gestation. Physical examination on Day 1 of life revealed many of the physical features of SLOS. Biochemical studies confirmed the prenatal diagnosis. The penis measured 1 × 0.7 cm, and was hooded and ventrally bound. He had a third-degree hvpospadias and a bifid scrotum. There was hyperpigmentation of the nipples and scrotum.Treatment with exogenous cholesterol (150 mg/kg/day) resulted in an increase in the size of the phallus to 2.3 × 1.2 cm in six weeks. Biochemical studies before and after therapy revealed the following cholesterol of 21.8 and 26 mg/dl, 7-DHC of 7.25 and 12 mg/dl; ACTH of 150 and 77 pg/ml; cortisol of 9.6 and 14 mcg/dl; testosterone of 48 and 153 ng/dl; and dihydrotestosterone of less than 2 and 38 ng/dl.We conclude that in males with SLOS treatment with cholesterol improves biosynthesis of cortisol and androgens, and enhances phallic growth.

Cholesterol Supplementation Enhances Growth of Phallus in Smith-Lemli-Opitz Syndrome † 444

Smith-Lemi-Opitz syndrome (SLOS) is an autosomal recessive inborn error of cholesterol biosynthesis due to a deficiency of the last enzyme of the cholesterol synthetic pathway, 7-dehydrocholesterol reductase. Affected patients have low concentrations of cholesterol and elevation of the cholesterol precursor, 7-dehydrocholesterol (7-DHC). Multiple congenital anomalies, dysmorphic facies, and growth and developmental retardation are common. Severely affected males have ambiguous genitalia. We believe that the genital anomalies seen in affected males are due to deficiency of androgens, but this has never been proven.

Clinical phenotype of desmosterolosis

We describe a child with lethal multiple malformations and generalised accumulation of desmosterol. The infant had macrocephaly, a hypoplastic nasal bridge, thick alveolar ridges, gingival nodules, cleft palate, total anomalous pulmonary venous drainage, ambiguous genitalia, short limbs, and generalised osteosclerosis. Gas chromatography-mass spectrometry demonstrated an abnormal accumulation of desmosterol in kidney, liver. and brain. Higher than normal levels of the same sterol were detected in plasma samples obtained from both parents. The biochemical phenotype in this infant is highly suggestive of a novel inborn error of cholesterol biosynthesis caused by an autosomal recessive deficiency of 3betahydroxysterol-delta24-reductase. A phenotypic overlap of this case with Raine syndrome was noted; however, desmosterol accumulation was not found on postmortem tissue samples from a previously reported case of this disorder.

Treatment of Smith-Lemli-Opitz syndrome: Results of a multicenter trial

Patients with the RSH or Smith-Lemli-Optiz syndrome (SLOS) have an inborn error of cholesterol biosynthesis which results in a deficiency of cholesterol and an elevation of the cholesterol precursor, 7-dehydrocholesterol. A treatment protocol consisting of administration of cholesterol +/- bile acids was initiated in an attempt to correct the biochemical abnormalities seen. Fourteen patients (8 female, 6 male: ages 2 months to 15 years) have now been treated for 6-15 months. Three patients received cholesterol alone, while 11 patients received cholesterol and one or more bile acids. Biochemical improvement in sterol levels and in the ratio of cholesterol to total sterols was noted in all patients. The most marked improvement was noted in patients presenting with initial cholesterol levels < 40 mg/dl. No toxicity was observed. Clinical improvement in growth and neurodevelopmental status was also observed.

Treatment of Smith‐Lemli‐Opitz syndrome: Results of a multicenter trial

Patients with the RSH or Smith-Lemli-Opitz syndrome (SLOS) have an inborn error of cholesterol biosynthesis which results in a deficiency of cholesterol and an elevation of the cholesterol precursor, 7-dehydrocholesterol. A treatment protocol consisting of administration of cholesterol ± bile acids was initiated in an attempt to correct the biochemical abnormalities seen. Fourteen patients (8 female, 6 male: ages 2 months to 15 years) have now been treated for 6–15 months. Three patients received cholesterol alone, while 11 patients received cholesterol and one or more bile acids. Biochemical improvement in sterol levels and in the ratio of cholesterol to total sterols was noted in all patients. The most marked improvement was noted in patients presenting with initial cholesterol levels <40 mg/dl. No toxicity was observed. Clinical improvement in growth and neurodevelopmental status was also observed. Am. J. Med. Genet. 68:311–314, 1997. © 1997 Wiley-Liss, Inc.

CORRELATION OF CLINICAL PHENOTYPE AND BIOCHEMICAL DEFECT IN SMITH-LEMLI-OPITZ SYNDROME (SLOS). • 480

SLOS is caused by an inborn error of cholesterol biosynthesis. Affected patients have growth and developmental retardation, congenital anomalies, and a characteristic facial appearance. Prior to discovery of the biochemical defect, diagnosis was based on clinical examination alone. Confirmation of the clinical diagnosis can now be accomplished by demonstration of the characteristic abnormal sterol pattern in plasma or other tissues.