Smith-Lemli-Opitz syndrome (SLOS)
Introduction
One of the most frequent AR syndromes in our population
(second after the cystic fibrosis). Genetically based
metabolic disorder of the cholesterol synthesis which cause
wide spectrum of congenital malformations and mental
retardation. Congenital malformations of the urogenital
tract are characteristic.
Etiology, pathogenesis
- incidence: 1 : 10 000 – 1 : 40 000
- carriers (heterozygotes): up to every 30th individual in the population
- deficit of one of the enzymes for the cholesterol synthesis
leads to its deficiency (disorders of cell
membranes construction, deficit of steroid hormones,
bile acids, myelinisation disorder) and causes structural
defects and disorders of the fetus masculinization
Clinical signs
Wide variability of symptomes of this syndrome:
- phenotypic features of the face (micrognathia, eyelid ptosis,
long philtrum and others) and limbs (syndactyly
of the 3rd and 4th toe, simian creases and others),
microcephaly and others.
- congenital malformations of the urogenital tract
(ambiguous genitalia and other serious malformations
of the external genitalia, agenesis, hypoplasia and
cystic renal dysplasia)
- congenital malformations of the central nervous system,
cleft palate, congenital heart defects etc.
- growth retardation
- Prognosis:
- fetuses are often spontaneously aborted or stillborn
- seriously afected newborns die during the first weeks
of life, the symptoms are multiorgan
failure, evetually heart defects, while less damaged
(with phenotypic features, minor congenital
malformation such as hypospadia, cryptorchidism, cleft palate)
can live to adult age.
- mental retardation, behavior disorders, failure to thrive
Prenatal diagnosis
- low estriol level in the screening triple test
- amniotic fluid examination of cholesterol level and
its precursors (metabolites such as 7-DHC are
remarkably elevated) in the 2nd trimester
- chorionic villi sampling (CVS) at the end of the 1st trimester
- ultrasound: congenital malformation of the fetus
Postnatally the cholesterol level in the serum and its precursors is examined
(cholesterol levels are low and the precursors are remarkably increased).
Case study
Smith-Lemli-Opitz syndrome (SLOS)
Marta Ježová
Introduction
Case of Smith-Lemli-Opitz sydrome in a male 22-week fetus.
Macroscopic appearance
- external features of the face:
- microcephaly
- long philtrum
- lowered corners of the mouth — fish mouth
- external genitalia malformation
SLOS, obličej (72458)
SLOS, zevní genitál (72459)
Pictures
SLOS, 22-week male fetus, general view:
SLOS, stigmatisation, Macro, autopsy (72457)
SLOS, external features of the face, side view (micrognathia):
SLOS, stigmatisation, micrognathia, Macro, autopsy (72458)
SLOS, external genitalia (hypospadia, ventral penis flexion):
Hypospadia, Macro, autopsy (72459)
Skin syndactyly of 2nd and 3rd toe (fork toe):
Syndactylia (fork-toe), Macro, autopsy (72460)
Syndactylia (fork-toe), Macro, autopsy (72461)
Case study
Smith-Lemli-Opitz syndrom (SLOS)
Marta Ježová
History
Female infant born at term with abnormal phenotypic
features. Corpus callosum agenesis had been diagnosed
prenatally. Prenatal karyotype was normal 46 XX. Pulmonary
hypertension persisted after birth. The child required
ventilation support and failured to thrive. Bilateral congenital
cataract was also identified. Attacks of malign arrythmia
(ventricular tachycardia, ventricular fibrilation) appeared
agonally. The child demised at 1 month of age.
Final diagnosis was made post mortem by DNA analysis:
Smith-Lemli-Opitz syndrome.
Direct DNA analysis was carried out in both parents and than the
deceased child to search for the most common mutations in the
7- dehydrocholesterol reductase gen (in Czech population).
The childs genotype was p. W151X/ IVS 8-1G>C.
The parents are healty
carriers of the mutations.
There is an entire deficiency of
the enzym with p. W151X mutation, the affected individuals do
not survive 1 month.
Macroscopic appearance
- external features: postnatal growth retardation, microcephaly,
receding forehead, flat occiput, deep-set eyes, broad nasal bridge,
low set ears, micrognathia, small tongue, short upper limbs, postaxial
polydactyly of the left lower limb, deformed feet (turned outward)
- brain malformation: microencephaly, partial corpus callosum agenesis, dilated
occipital horns of the lateral ventricles
- heart defect: patent ductus arteriosus, right ventricle hypertrophy
- abnormal lobation of lungs (there was no lobation at all)
- icterus, hepatomegaly, intrahepatal cholestasis
SLOS, face (73067)
Hexadactyly (73068)
Pictures
Icterus, microcephaly, short upper limbs, feet deformity:
SLOS, Macro, autopsy (73066)
Microcephaly, flat occiput, receding forehead, low-set ears, mild micrognathia:
SLOS, Macro, autopsy (73067)
Hexadactyly:
SLOS, Macro, autopsy (73068)
Broad nasal bridge, deep set eyes:
SLOS, Macro, autopsy (73069)