New Face of Smith-Lemli-Opitz Syndrome

Overview

Smith-Lemli-Opitz syndrome is after the discovery of G. S. Tint (Amer. J. Med. Genet., 47, 1993, 573-574)a new metabolic-malformation syndrome with an exactly defined impairment of the cholesterol biosynthesis,deficiency of 7-dehydrocholesterol reductase. The authors analyzed the clinical symptoms and biochemical findingsof eight patients with the diagnosis of SLOS, according to the karyotype in 4 girls and 4 boys aged 3 weeks to 7years. The total serum, cholesterol concentration assessed by the usual enzymatic method CHOD-PAP varied inindividual patients within the range from 0.34 - 2.42 mmol/l. In 7 patients by means of ultraviolet spectrophoto-metry of serum lipids an absorption spectrum typical for accumulation of 7-dehydrocholesterol was found.Quantitative examination of serum sterols by gas chromatography and mass spectrometry (GC-MS) was used inthese patients to assess markedly reduced total serum cholesterol concentrations of 0.017 - 1.5 mmol/l, andextremely elevated concentrations of its precursors 7-dehydrocholesterol of 0.20 - 0.60 mmol/l and its isomer8-dehydrocholesterol of 0.23 - 0.59 mmol/l. In the group also a 6-week-old boy was included who had typical clinicalsymptoms and as to biochemical examinations only a very low cholesterol value of 0.34 mmol/l was detected bythe common enzymatic method. The cholesterol concentration of 0.017 mmol/l in a 3-week-old neonate witha serious clinical symptomatology who died at the age of 23 days is, according to the authors knowledge, the hithertolowest described cholesterol value in man. As to clinical symptoms in children the following dominated: hypotonia,failure to thrive, mental retardation, intrauterine growth retardation, microcephaly, cleft palate, syndactyly of the 2nd - 3 rd toe, micrognathia, cardiac defects, postaxial polydactyly and genital abnormalities. In one instancea prenatal diagnosis was made in a mother whose first child suffered from biochemically confirmed SLOS. Analysisof sterols in amniotic fluid revealed that the foetus does not suffer from 7-dehydrocholesterol reductase deficiency.In two patients cholesterol substitution treatment was started, 50 mg/kg/day, and ursodeoxycholic acid, 15mg/kg/day.SLOS is not a rare disease. The authors assume a prevalence of 1 : 15 - 20 000 of liveborn infants in Slovakia.In the conclusion they emphasize that for the diagnosis of SLOS no longer clinical symptoms suffice. It is essentialto provide biochemical evidence of cholesterol precursors. Where this is not possible for technical reasons, theauthors recommend a relatively simple screening method of ultraviolet spectrophotometry of serum lipids.

Key words:
Smith-Lemli-Opitz syndrome, 7-dehydrocholesterol reductase deficiency, hypocholesterolaemia,ultraviolet spectrophotometry of serum lipids, clinical symptoms, prevalence, treatment