Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0917816 (mental retardation)
 15,867 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Characterization of liver involvement in defects of cholesterol biosynthesis: long-term follow-up and review. 1558 Jun 35

While excess cholesterol may have deleterious consequences, as in the case of atherosclerosis, too little cholesterol may endanger the development of the brain. Different degrees of mental retardation are often observed in inborn errors of cholesterol synthesis, such as the Smith-Lemli-Opitz syndrome or in maternal phenylketonuria, where the metabolite of accumulating phenylalanine, phenylacetate, is an inhibitor of cholesterol synthesis. Lack of cholesterol during brain development as a consequence of these genetic defects leads to severe brain damage, microencephaly and mental retardation, which are also hallmarks of the fetal alcohol syndrome (FAS). The brain relies on the in situ synthesis of cholesterol, which occurs mostly in astrocytes. Astrocyte-produced cholesterol is utilized for cell proliferation, or is released, via astrocyte-secreted high density lipoprotein-like particles containing apolipoprotein E, outside the cell, where it is taken up and utilized by neurons for dendrite outgrowth and to form synapses. We propose the hypothesis that ethanol may disrupt cholesterol homeostasis during brain development, and that this effect may be responsible, at least in part, for the central nervous system dysfunctions observed in the FAS, which include altered astrocyte proliferation, neuronal death and diminished synaptic contacts.
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PMID:Disruption of cholesterol homeostasis in the developing brain as a potential mechanism contributing to the developmental neurotoxicity of ethanol: an hypothesis. 1561 67

In the final step of cholesterol synthesis, 7-dehydrocholesterol reductase (DHCR7) reduces the double bond at C7-8 of 7-dehydrocholesterol to yield cholesterol. Mutations of DHCR7 cause Smith-Lemli-Opitz syndrome (SLOS). Over 100 different mutations of DHCR7 have been identified in SLOS patients. SLOS is a classical multiple malformation, mental retardation syndrome, and was the first human malformation syndrome shown to result from an inborn error of cholesterol synthesis. This paper reviews the biochemical, molecular, and mutational aspects of DHCR7.
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PMID:3beta-hydroxysterol Delta7-reductase and the Smith-Lemli-Opitz syndrome. 1567 Jul 17

The Smith-Lemli-Opitz syndrome (SLOS) is a phenotypically variable metabolic malformation and mental retardation syndrome for which more than 80 mutations in the DHCR7 disease-causing gene have been described. The DHCR7 mutational spectra differ significantly in different areas of Europe, and several common putative founder mutations account for a substantial fraction of all mutations in some ethnic groups. Here we have analysed 47 SLOS patients and describe 14 newly identified mutations in 18 SLOS patients of Ashkenazi Jewish, Austrian, British, German, Italian, Irish, Polish, Portuguese, and Spanish origins. Half of the new mutations are in the transmembrane domains of the protein. In addition, there were two null mutations, one mutation in the 4th cytoplasmic loop, two mutations in the first and last codons, and three mutations in other regions such as the second cytoplasmic loop and the first endoplasmic loop. The analysis included 20 Spanish and 12 Italian SLOS patients and revealed very different mutation spectra in these patients compared to previously described patients from Czechoslovakia, Germany, Poland, and the UK and implicated p.Thr93Met on the J haplotype as the most frequent Mediterranean founder mutation.
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PMID:Identification of 14 novel mutations in DHCR7 causing the Smith-Lemli-Opitz syndrome and delineation of the DHCR7 mutational spectra in Spain and Italy. 1577 24

Smith-Lemli-Opitz syndrome (SLOS) is a syndrome of rare multiple congenital anomalies/mental retardation associated with low plasma cholesterol levels. Prior to receiving the diagnosis of SLOS, affected children may present as a neonatal surgical emergency with ambiguous genitalia, Hirschsprung's disease, and pyloric stenosis. We present two fatal cases of SLOS with near-total Hirschsprung's disease; the surgical, anaesthetic, and medical aspects of the cases are discussed, and a literature review is presented.
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PMID:Surgical implications of the Smith-Lemli-Opitz syndrome. 1583 78

In humans, genetic disorders affecting post-squalene cholesterol biosynthesis result in a variety of dysmorphology syndromes. One key feature of all of these is the presence of mental retardation and another is the lack of a robust genotype-phenotype correlation. Knockout mice defective in the 3beta hydroxysterol Delta7 reductase (Dhcr7), a model for the most common of such disorders in humans, the Smith-Lemli-Opitz syndrome, all die within 24 h of birth. The cause of this postnatal mortality in these mice has not been fully established. In the present study, we tested the hypothesis that CNS dysfunction was a major cause of this lethality and investigated whether transgenic expression of normal human DHCR7 in neuronal tissues could rescue this neonatal lethality. Transgenic mice, expressing DHCR7 driven by murine nestin promoter, were bred onto Dhcr7 knock-out (Dhcr7(-1-)) background and resulted in a partial rescue of neonatal lethality in 11 of 91 (12%) of transgene-positive Dhcr7(-1-) pups. Despite biochemical analyses that showed continued profound cholesterol deficiency in brain, rescued animals survived between 3 and 17 days. Thus, one important conclusion to be drawn is that defects in CNS in Dhcr7 knockout mice may contribute to the early lethality. Another conclusion is that even small and subtle changes in the brain sterol metabolism were sufficient to enable rescue. These data also provide important clues as to the cause of the variable expressivity seen in SLOS.
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PMID:Partial rescue of neonatal lethality of Dhcr7 null mice by a nestin promoter-driven DHCR7 transgene expression. 1586 27

Smith-Lemli-Opitz syndrome is a rare autosomal recessive disorder characterized by multiple congenital anomalies and various degrees of cognitive deficits. This condition results from a deficiency of 7-dehydrocholesterol reductase, a critical step in cholesterol biosynthesis. Children with Smith-Lemli-Opitz syndrome have frequent infections, particularly of the respiratory tract. Immunodeficiency, however, is not recognized as a part of this metabolic condition. Frequent infections are usually attributed to a decreased patient mobility and reduced respiratory effort secondary to muscular hypotonia and mental retardation, which are often present in affected individuals. We describe a patient with Smith-Lemli-Opitz syndrome and recurrent respiratory infections who was found to have a selective antibody deficiency. The immunological diagnosis was based on an absent immune response to Pneumovax. She also had no immunological response to hepatitis B vaccine and was unable to break down red cells with isoagglutinin B. Therapy with intravenous IgG (IVIG) was initiated. Infections were less severe, although they still occurred in a high frequency after initiation of the IVIG therapy. This finding prompts the need for a higher index of suspicion for an underlying immune deficiency in patients with Smith-Lemli-Opitz syndrome who present with recurrent and chronic infections. Early recognition and appropriate therapeutic interventions may decrease the severity of infections, prevent potentially fatal infections, and eventually improve the quality of life in these patients.
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PMID:Selective antibody immune deficiency in a patient with Smith-Lemli-Opitz syndrome. 1587 7

Smith-Lemli-Opitz syndrome (SLO) is an autosomal recessive disorder characterised by craniofacial dysmorphism, mental retardation, multiple congenital anomalies, and increased levels of 7-dehydrocholesterol (7-DHC) in body tissues and fluids. SLO is caused by mutations in the DHCR7 gene which encodes 7-dehydrocholesterol reductase, the last enzyme of cholesterol biosynthesis pathway. In our investigation, we screened 682 dysmorphic/mentally retarded Portuguese patients for abnormal levels of 7-DHC in blood by UV spectrometry. We identified six unrelated patients with SLO (0.87% of total). Mutational analysis of the DHCR7 gene led to the identification of seven distinct mutations, three of which are new (F174S, H301R, and Q98X). The common IVS8-1G > C and T93M variants together with the H301R accounted for 70% of the all SLO alleles in our population. Our findings contribute to the variegate array of pathological changes in the DHCR7 gene among different European populations.
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PMID:Molecular studies in Portuguese patients with Smith-Lemli-Opitz syndrome and report of three new mutations in DHCR7. 1597 35

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive malformation syndrome characterized by microcephaly, syndactyly of toes, ambiguous genitalia, and mental retardation. The underlying DHCR7 gene has been identified and a wide variety of distinct mutations were reported in USA and European SLOS patients. A significant difference has been suggested in the frequency of SLOS among different ethnic populations. Here, we report mutational analysis of seven Japanese SLOS patients. Five mutations, R352Q, R242H, G303R, X476Q, and S192F, were identified, and R352Q appeared most frequent, since nine out of the 13 mutations of Japanese origin were the same R352Q. These results suggest that R352Q is a predominant founder mutation in Japanese SLOS patients.
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PMID:R352Q mutation of the DHCR7 gene is common among Japanese Smith-Lemli-Opitz syndrome patients. 1604 99

[Nguyen et al. (2003); Am J Med Genet 121A: 109-112] reported a boy with severe hypocholesterolemia due to autosomal dominant hypobetalipoproteinemia (ADBHL) associated with severe growth retardation, mental deficiency, epicanthal folds, a short nose with low nasal bridge and anteverted nares and bilateral partial cutaneous syndactyly of toes 2 and 3. Many of these manifestations resembled those in a mild form of Smith-Lemli-Opitz syndrome (SLOS). We report on a 13-year-old boy with ADHBL, who manifested a SLOS-like phenotype, including mental retardation and a characteristic face, similar to that of a patient reported by [Nguyen et al. (2003); Am J Med Genet 121A: 109-112]. Our patient supports the hypothesis by [Nguyen et al. (2003); Am J Med Genet 121A: 109-112] that ADHBL induced cholesterol deficiency has a significant effect on morphogenesis during embryogenesis, although additional genetic or environmental factors may be required to develop an SLOS-like phenotype in individuals with ADHLB. This is a second case of Nguyen syndrome.
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PMID:An MCA/MR syndrome with hypocholesterolemia due to familial hypobetalipoproteinemia: report of a second patient with Nguyen syndrome. 1608 30


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