RESUMEN
The Smith-Lemli-Opitz syndrome (SLOS) is a multiple malformation/mental retardation syndrome caused by a deficiency of the enzyme 7-dehydrocholesterol Delta(7)-reductase. This enzyme converts 7-dehydrocholesterol (7-DHC) to cholesterol in the last step in cholesterol biosynthesis. The pathology of this condition may result from two different factors: the deficiency of cholesterol itself and/or the accumulation of precursor sterols such as 7-DHC. Although cholesterol synthesis is defective in cultured SLOS cells, to date there has been no evidence of decreased whole body cholesterol synthesis in SLOS and only incomplete information on the synthesis of 7-DHC and bile acids. In this first report of the sterol balance in SLOS, we measured the synthesis of cholesterol, other sterols, and bile acids in eight SLOS subjects and six normal children. The diets were very low in cholesterol content and precisely controlled. Cholesterol synthesis in SLOS subjects was significantly reduced when compared with control subjects (8.6 vs. 19.6 mg/kg per day, respectively, P < 0.002). Cholesterol precursors 7-DHC, 8-DHC, and 19-nor-cholestatrienol were synthesized in SLOS subjects (7-DHC synthesis was 1.66 +/- 1.15 mg/kg per day), but not in control subjects. Total sterol synthesis was also reduced in SLOS subjects (12 vs. 20 mg/kg per day, P < 0.022). Bile acid synthesis in SLOS subjects (3.5 mg/kg per day) did not differ significantly from control subjects (4.6 mg/kg per day) and was within the range reported previously in normals. Normal primary and secondary bile acids were identified. This study provides direct evidence that whole body cholesterol synthesis is reduced in patients with SLOS and that the synthesis of 7-DHC and other cholesterol precursors is profoundly increased. It is also the first reported measure of daily bile acid synthesis in SLOS and provides evidence that bile acid supplementation is not likely to be necessary for treatment. These sterol balance studies provide basic information about the biochemical defect in SLOS and strengthen the rationale for the use of dietary cholesterol in its treatment.
Asunto(s)
Ácidos y Sales Biliares/metabolismo , Colesterol/metabolismo , Síndrome de Smith-Lemli-Opitz/metabolismo , Esteroles/sangre , Adolescente , Preescolar , Colesterol en la Dieta , Femenino , Humanos , Lactante , Masculino , Valores de Referencia , Síndrome de Smith-Lemli-Opitz/sangreRESUMEN
Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive condition comprising multiple malformations, mental retardation, and growth failure, results from reduced activity of the final enzyme in cholesterol biosynthesis, 7-dehydrocholesterol Delta(7)-reductase (DHCR7). Reduced plasma and tissue cholesterol concentrations and accumulation of cholesterol precursors including 7-dehydrocholesterol (7-DHC) are characteristic biochemical abnormalities. While it is still unclear what role these potentially toxic precursors have in the pathogenesis of this disorder, the accumulation of 7-DHC in the brain has been associated with impaired learning in rats and oxidized 7-DHC has been shown to induce growth retardation in cultured rat embryos. We hypothesized that supplemental dietary cholesterol would increase plasma cholesterol levels and suppress synthesis of 7-DHC and other abnormal sterols in individuals with SLOS. After baseline sterol levels were obtained, patients were provided supplemental cholesterol as egg yolk. Plasma sterols were analyzed by capillary-column gas chromatography over time in four children with SLOS. When evaluated at 4-8 weeks after the initiation of cholesterol supplementation, there was a marked increase in mean plasma cholesterol, from 53 mg/dl to 82 mg/dl. While the percent of total sterols as 7-DHC decreased from 15% to 10%, there was no change in total plasma 7-DHC levels. However, when evaluated 35-90 weeks after the institution of cholesterol supplementation, mean plasma 7-DHC decreased, from 11.3 mg/dl to 3.5 mg/dl (-67%, P < 0.05), along with an increase in mean plasma cholesterol from 53 mg/dl to 114 mg/dl (+116%, P < 0.05). These results support the hypothesis that over time dietary cholesterol supplementation from egg yolk increases the plasma cholesterol levels and decreases levels of 7-DHC which may be toxic. These data have important therapeutic implications in the management of SLOS.
Asunto(s)
Colesterol en la Dieta/metabolismo , Colesterol/sangre , Deshidrocolesteroles/sangre , Yema de Huevo/metabolismo , Síndrome de Smith-Lemli-Opitz/terapia , Colesterol en la Dieta/administración & dosificación , Femenino , Humanos , Lactante , Masculino , Síndrome de Smith-Lemli-Opitz/sangre , Síndrome de Smith-Lemli-Opitz/metabolismoRESUMEN
An 4-mo-old male was found to have an isolated increase in 2-methylbutyrylglycine (2-MBG) and 2-methylbutyrylcamitine (2-MBC) in physiologic fluids. In vitro oxidation studies in cultured fibroblasts using 13C- and 14C-labeled branched chain amino acids indicated an isolated block in 2-methylbutyryl-CoA dehydrogenase (2-MBCDase). Western blotting revealed absence of 2-MBCDase protein in fibroblast extracts; DNA sequencing identified a single 778 C>T substitution in the 2-MBCDase coding region (778 C>T), substituting phenylalanine for leucine at amino acid 222 (L222F) and absence of enzyme activity for the 2-MBCDase protein expressed in Escherichia coli. Prenatal diagnosis in a subsequent pregnancy suggested an affected female fetus, supporting an autosomal recessive mode of inheritance. These data confirm the first documented case of isolated 2-MBCDase deficiency in humans.
Asunto(s)
Errores Innatos del Metabolismo de los Aminoácidos/diagnóstico , Isoleucina/metabolismo , Oxidorreductasas actuantes sobre Donantes de Grupo CH-CH , Oxidorreductasas/sangre , Errores Innatos del Metabolismo de los Aminoácidos/sangre , Secuencia de Bases , Carnitina/análogos & derivados , Carnitina/sangre , Cartilla de ADN , ADN Complementario , Femenino , Humanos , Lactante , Masculino , Oxidorreductasas/genética , Embarazo , Diagnóstico PrenatalRESUMEN
Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive condition with multiple malformations, mental retardation, and growth failure, results from markedly reduced activity of the final enzyme in the cholesterol biosynthetic pathway, 7-dehydrocholesterol Delta(7)-reductase (DHCR7). We diagnosed SLOS in a fetus following intrauterine demise at 32 weeks' gestation. Chorionic villus (CV) sampling had been performed at 30 weeks because oligohydramnios and atrioventricular septal defect were noted on fetal ultrasound. On fetal post-mortem examination, a midline U-shaped soft palate cleft, micrognathia, postaxial polydactyly of the fingers with single transverse palmar creases bilaterally, and cutaneous syndactyly of toes two-three bilaterally suggested SLOS. We hypothesized that SLOS could be confirmed by analysis of tissue sterols despite extensive autolysis, and by measurement of enzyme activity in CV cells. Measurement of DHCR7 activity in CV cells was undertaken using ergosterol as a substrate. CV cells were unable to convert any ergosterol to brassicasterol after a 72 h incubation period while control CV cells reduced 12.6-71.8% of ergosterol to brassciasterol in a 72 h period. SLOS was confirmed by measurement of elevated 7-dehydrocholesterol (7-DHC) in the CV cells. Measurements of sterols were made in multiple fetal tissues. All tissues analysed showed elevated 7-DHC with markedly increased 7-DHC/cholesterol ratios.
Asunto(s)
Muestra de la Vellosidad Coriónica , Vellosidades Coriónicas/enzimología , Muerte Fetal , Oxidorreductasas actuantes sobre Donantes de Grupo CH-CH , Oxidorreductasas/deficiencia , Síndrome de Smith-Lemli-Opitz/diagnóstico , Esteroles/análisis , Adulto , Colesterol/análisis , Deshidrocolesteroles/análisis , Ergosterol/metabolismo , Femenino , Edad Gestacional , Humanos , Oxidorreductasas/análisis , Oxidorreductasas/metabolismo , Embarazo , Ultrasonografía PrenatalRESUMEN
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.
Asunto(s)
Cromosomas Humanos Par 11/genética , Oxidorreductasas actuantes sobre Donantes de Grupo CH-CH , Oxidorreductasas/genética , Síndrome de Smith-Lemli-Opitz/genética , Alelos , Secuencia de Aminoácidos , Arabidopsis/enzimología , Secuencia de Bases , Línea Celular , Colesterol/análisis , Mapeo Cromosómico , Clonación Molecular , Análisis Mutacional de ADN , Deshidrocolesteroles/metabolismo , Humanos , Datos de Secuencia Molecular , ARN Mensajero/análisis , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Transfección/genéticaRESUMEN
PURPOSE: To describe the ophthalmologic findings and electroretinograms in patients with microcephaly and chorioretinal degeneration. METHODS: We reviewed the hospital records of 20 patients with microcephaly that was not part of a recognizable syndrome prior to initial referral to the institutional consultative practice of one of the authors (RGW). Twelve patients, all from separate families, were diagnosed as having microcephaly with chorioretinopathy. Ten of these patients had ISCEV-standard electroretinograms (ERG). RESULTS: No family history of microcephaly or retinal degeneration was found in any of our patients. Three patients had another family member with mental retardation. Three of the 12 were compatible with the autosomal dominant form of microcephaly with chorioretinopathy (MIM 156590), possibly as a new mutation. Eight patients, who had fundus findings of retinitis pigmentosa, were similar to the autosomal recessive form of microcephaly with chorioretinal degeneration (MIM 251270). The ERGs were moderately to severely subnormal for responses of both rods and cones. The retinal findings varied from no pigmentary changes, pigment clumping and bone spicules, pigmentary granularity, bull's eye maculopathy, choroidal and retinal atrophy, to lacunar depigmentation. Mental retardation was mild to profound. The abnormal findings from MRI/ CT brain scans (8 patients) were cerebellar atrophy (2), agenesis of cerebellar vermis (1), cortical atrophy (1), and pachygyria (1). Dysmorphic features were present in most patients. Chromosome studies were normal, except for one patient with ring chromosome 14. CONCLUSIONS: Although the patients reviewed in this study represent a heterogeneous group of disorders, ocular abnormalities, especially retinal degeneration, are frequent among patients with microcephaly.
Asunto(s)
Enfermedades de la Coroides/complicaciones , Microcefalia/complicaciones , Degeneración Retiniana/complicaciones , Adolescente , Niño , Preescolar , Electrorretinografía , Femenino , Fondo de Ojo , Humanos , Lactante , Masculino , Degeneración Retiniana/patología , Degeneración Retiniana/fisiopatología , Agudeza Visual/fisiologíaRESUMEN
We evaluate the ophthalmologic findings in 8 children with RSH/Smith-Lemli-Opitz syndrome (SLOS) and document abnormal concentrations of cholesterol and cholesterol precursors in the ocular tissues in a case of SLOS. The most common ophthalmologic finding was blepharoptosis, which was found in 6 of 8 patients, with the severity ranging from mild to moderate. None of the patients in the present study demonstrated cataracts; none had amblyopia from blepharoptosis. One patient had a right hypertropia with overaction of the inferior oblique muscle. This patient also had optic atrophy and a second patient had bilateral optic nerve hypoplasia. The importance of these findings to the visual function remains to be defined. Sterol analysis from ocular tissues of an aborted fetus with SLOS showed increased 7- and 8-dehydrocholesterol and a low cholesterol concentration in the retinal pigment epithelium, lens, cornea, and sclera. Routine ophthalmologic examination is indicated in SLOS because of the high incidence of abnormalities, most likely due to the abnormal synthesis of cholesterol and cholesterol precursors in the ocular tissues of these patients, as evidenced by sterol analysis of the ocular tissues in a case of SLOS.
Asunto(s)
Anomalías del Ojo/genética , Síndrome de Smith-Lemli-Opitz/genética , Preescolar , Colesterol/biosíntesis , Femenino , Humanos , Lactante , Recién Nacido , Masculino , Estudios Prospectivos , Síndrome de Smith-Lemli-Opitz/metabolismo , Esteroles/metabolismoRESUMEN
STUDY OBJECTIVES: To determine the feasibility of Pap screening and follow-up of urban emergency department patients and the prevalence of cervical dysplasia and carcinoma in this group. DESIGN: During a four-month period, Pap smears were added to pelvic examinations performed in the ED. Follow-up, including repeat Pap smear or biopsy, was attempted on all abnormal smears. SETTING: Urban county hospital-based ED. INTERVENTIONS: Pap screening and follow-up. RESULTS: Dysplasia was present in 8% of screening Pap smears. Eighty-two percent of patients with dysplasia on screening Pap smear returned for follow-up. Four percent of screened patients received a confirmed diagnosis of CIN 1 or more following repeat Pap smear or biopsy. Two invasive cervical cancers were identified. CONCLUSIONS: There is a high prevalence of cervical dysplasia among women screened with Pap smears in an urban ED. Routine Pap screening in urban EDs can be an important component of cervical cancer control programs for high-risk women.