Lambotte syndrome: microcephaly, holoprosencephaly, intrauterine growth retardation, facial anomalies, and early lethality--a new sublethal multiple congenital anomaly/mental retardation syndrome in four sibs

Wolf-Hirschhorn syndrome: Prenatal diagnosis and molecular cytogenetic characterization of a de novo distal deletion of 4p (4p16.1 → pter) in a fetus with facial cleft and preaxial polydactyly

OBJECTIVE

We present prenatal diagnosis and molecular cytogenetic characterization of Wolf-Hirschhorn syndrome (WHS) in a fetus with facial cleft and preaxial polydactyly.

MATERIALS AND METHODS

A 37-year-old woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age, and the result showed an aberrant chromosome 4 or 46,XX,add(4) (p15.3). The woman consulted our clinics at 22 weeks of gestation and requested for repeat amniocentesis. Prenatal ultrasound revealed intrauterine growth restriction, facial cleft, vermian hypoplasia of cerebellum, micrognathia and absent stomach. Conventional cytogenetic analysis was performed on cultured amniocytes, parental bloods and cord blood. Array comparative genomic hybridization (aCGH) and quantitative fluorescent polymerase chain reaction (QF-PCR) were performed on the DNAs extracted from uncultured amniocytes and parental bloods. Fluorescence in situ hybridization (FISH) analysis was performed on cultured metaphase amniocytes.

RESULTS

aCGH analysis on uncultured amniocytes revealed arr 4p16.3p16.1 (74,447-8,732,731) × 1.0 [GRCh37 (hg19)] with an 8.66-Mb deletion of 4p16.3-p16.1 encompassing 70 [Online Mendelian Inheritance of in Man (OMIM)] genes including ZNF141, FGFRL1, TACC3, LETM1, NSD2 and NELFA. QF-PCR revealed a paternal origin of the distal 4p deletion. Conventional cytogenetic analysis revealed 46,XX,del(4) (p16.1)dn in the fetus. Metaphase FISH analysis confirmed a 4p16 deletion. The parental karyotypes were normal. The pregnancy was subsequently terminated, and a malformed fetus was delivered with typical WHS facial dysmorphism, bilateral cleft lip and palate, and preaxial polydactyly on the right hand.

CONCLUSION

aCGH, QF-PCR and FISH help to delineate the nature of a prenatally defected aberrant chromosome, and the acquired information is useful for genetic counseling.

Syndromes associated with holoprosencephaly

Holoprosencephaly (HPE) is partial or complete failure of the forebrain to divide into hemispheres and can be an isolated finding or associated with a syndrome. Most cases of HPE are associated with a syndrome and roughly 40%-60% of fetuses with HPE have trisomy 13 which is the most common etiology of HPE. Other syndromes associated with HPE include additional aneuploidies like trisomy 18 and single gene disorders such as Smith-Lemli-Opitz syndrome. There are a number of syndromes such as pseudotrisomy 13 which do not have a known molecular etiology; therefore, this review has two parts: syndromes with a molecular diagnosis and syndromes where the etiology is yet to be found. As most HPE is syndromic, this review provides a comprehensive list and description of syndromes associated with HPE that may be used as a differential diagnosis and starting point for evaluating individuals with HPE.

Semilobar holoprosencephaly in a 12-month-old baby boy born to a primigravida patient with type 1 diabetes mellitus: a case report

Background

Holoprosencephaly is a rare spectrum of cephalic disorders resulting from a failure or incomplete division of the embryonic forebrain into distinct cerebral hemispheres. It is the most common brain malformation with an incidence of 1:250 during embryogenesis; however, owing to the associated high rates of spontaneous abortion the incidence is 1:16,000 among live deliveries. Pathogenesis of holoprosencephaly is complex and heterogeneous involving genetic abnormalities, teratogenic exposures, and syndromic associations. Among the teratogenic exposures, maternal diabetes is a well-established risk factor associated with a 200-fold increased incidence of holoprosencephaly.

Case presentation

We report a case of a delayed diagnosis of semilobar holoprosencephaly in a 12-month-old baby boy of African descent who presented to us with a history of global developmental delay, erratic sleep patterns, and poor weight gain. He was born to a type 1 diabetes mellitus mother at 39+ weeks by emergency cesarean section due to fetal distress and breech presentation. The baby weighed 2315 g and had Apgar scores of 6/10 and 8/10 at 1 and 5 minutes respectively. A physical examination done at 12 months of age revealed a small-for-age child with a developmental age of 2 months. He had normal facies but a neurological examination revealed hypotonia in all four limbs. The rest of systemic examination was unremarkable. Hematological and biochemical investigations revealed normal findings except for iron deficiency anemia. The child also underwent magnetic resonance imaging of his brain which revealed distinctive features of semilobar holoprosencephaly. He was treated for iron deficiency anemia with Hemovit syrup (ferric ammonium citrate, folic acid, pyridoxine hydrochloride, cyanocobalamin, and zinc sulfate) 10 ml thrice daily, ferrous sulfate 10 mg once daily, folic acid 1 mg once daily, and multivitamin syrup 5 ml once daily. Furthermore, nutritional and genetic counseling was offered to his parents.

Conclusions

In conclusion, although rare, holoprosencephaly is the commonest structural anomaly of the brain with a complex and multifactorial etiopathogenesis. It is prudent to diagnose it prenatally, classify its severity, and forge its prognosis so that parents are counseled early enough to make informed decisions especially where termination of pregnancy may be implicated.

Telomeres: a diagnosis at the end of the chromosomes

In recent years, subtelomeric rearrangements have been identified as a major cause of mental retardation and/or malformation syndromes. So far, over 2500 subjects with mental retardation have been tested and reported of whom approximately 5% appeared to have a subtelomeric rearrangement. In this review, the clinical aspects of each known (submicroscopic) subtelomeric deletion will be presented and the various methods available for detecting subtelomeric abnormalities will be discussed. Not only will the patients and their families benefit from a good collection and report of the various telomeric abnormalities and their clinical phenotype, but it will also give more insight into the aetiology of mental retardation and malformation syndromes.

Chromosome imbalances associated with epilepsy

Epilepsy is among the most frequent findings in many, especially autosomal, chromosome aberrations. Its incidence, however, is very variable, and there are very few aberrations in which epilepsy is a constant finding. Even siblings and monozygotic twins with the same aberration are often discordant for seizure disorders. Similar observations can be made for congenital (major) malformations in chromosome aberrations. The common explanation is that in these instances epilepsy is not caused by the action of a single gene in single or triple dose, but is influenced by the combined action of a number of genes within and outside of the aneuploid segment. The situation is comparable to a polygenic model of inheritance. Gene mutations associated with epilepsy are known, to date, only for two disorders: the lissencephaly 1 gene in Miller-Dieker syndrome and mutations in the UBE3A gene in Angelman syndrome. Chromosome aberrations in which epilepsy is a major and consistent finding include Angelman syndrome due to loss of the maternal 15q11.2-q12 segment, tetrasomy of the maternal segment 15pter-q13 due to an additional inv dup chromosome, Miller-Dieker syndrome due to deletion of the 17p13.3 segment including the lissencephaly1 gene, ring chromosome 20, and Wolf-Hirschhorn syndrome due to deletion of at least the 4p16.3 segment.

Brains and faces in holoprosencephaly: pre- and postnatal description of 30 cases

OBJECTIVE

To investigate the prenatal appearance of the holoprosencephaly spectrum.

METHODS

A database of 1750 fetuses with congenital anomalies identified by ultrasound was prospectively collected from 1987 to 2000. Among them, 30 cases (1.7%) with holoprosencephaly were prenatally identified and described.

RESULTS

The prevalence of holoprosencephaly in the Health Region of the National Center for Fetal Medicine in Norway was 1.26 : 10 000; the sex distribution (male : female) was 1.4 : 1. Holoprosencephaly was found in one dichorionic twin pregnancy and one pair of conjoined twins. Among the 30 cases of holoprosencephaly, 18 were alobar, five were semilobar, two were lobar, two were lobar variants, and three were anencephalic. The facial features varied considerably. Sixty-seven per cent (20/30) had associated structural anomalies that were not related to the cerebral and facial holoprosencephaly condition. Thirty-seven per cent (11/30) had detectable chromosome aberrations and 23% (7/30) had nonchromosomal syndromal origin. The size or shape of the head was abnormal in 83% (25/30) of holoprosencephaly cases.

CONCLUSION

This study indicates that holoprosencephaly represents a heterogeneous entity with different etiologies and clinical appearances. The fact that holoprosencephaly features are found associated with particular conditions such as fronto-nasal dysplasia (2/30; 6.7%), agnathia-otocephaly (3/30; 10%), and anencephaly (3/30; 10%), suggests that these may be underreported conditions in other large holoprosencephaly series.

Holoprosencephaly associated with an apparent isolated 2q37.1-->2q37.3 deletion

A female infant survived 5(1/2) hours after delivery at 33 weeks gestation. Autopsy showed a lobar variant of holoprosencephaly (HPE). Cytogenetic analysis revealed a 2q37.1-->2q37.3 deletion. This case represents the fourth reported case of HPE associated with partial monosomy 2q37 and the first with an apparent isolated 2q37 deletion. Chromosome segment 2q37.1-->2q37.3 may harbor yet another locus important in forebrain development, which, when disrupted, can lead to brain malformations within the HPE spectrum.

Towards a greater understanding of the pathogenesis of holoprosencephaly

Holoprosencephaly is a malformation of the cerebral hemispheres resulting in the absence of the inter-hemispheric fissure along with other defects of brain development. Frequently midline defects of the craniofacial structures are also present. This malformation sequence has been of interest for many years because of the well recognized genetic and environmental pathogeneses, although the molecular pathogenesis remained elusive. Recent studies have begun clarifying the molecular pathogenesis of holoprosencephaly. Herein is reviewed the syndromes associated with holoprosencephaly, the pathology of this disorder, genetic and environment factors, and a current understanding of the molecular pathogenesis of this disorder.

Holoprosencephaly: from Homer to Hedgehog

Holoprosencephaly (HPE), a common developmental defect affecting the forebrain and face, is etiologically heterogeneous and exhibits wide phenotypic variation. Graded degrees of severity of the brain malformation are also reflected in the highly variable craniofacial malformations associated with HPE. In addition, individuals with microforms of HPE, who usually have normal cognition and normal brain imaging, are at risk for having children with HPE. Some obligate carriers for HPE may not have any phenotypic abnormalities. Recurrent chromosomal rearrangements in individuals with HPE suggest loci containing genes important for brain development, and abnormalities in these genes may result in HPE. Recently, Sonic Hedgehog (SHH) was the first gene identified as causing HPE in humans. Proper function of SHH depends on cholesterol modification. Other candidate genes that may be involved in HPE include components of the SHH pathway, elements involved in cholesterol metabolism, and genes expressed in the developing forebrain.

Private multiple congenital anomaly syndromes may result from unbalanced subtle translocations: t(2q;4p) explains the Lambotte syndrome

In 1990, Lambotte syndrome was reported as an apparently autosomal recessive multiple congenital anomaly/mental retardation (MCA/MR) syndrome observed in 4 of 12 sibs from a probably consanguineous mating [Verloes et al., Am J Med Genet 1990; 37:119-123]. Major manifestations included intrauterine growth retardation (IUGR), microcephaly, large soft pinnae, hypertelorism, beaked nose, and extremely severe neurologic impairment, with holoprosencephaly in one instance. After the observation of a further affected child born of one unaffected sister, in situ hybridization analysis and chromosome painting techniques demonstrated a subtle t(2;4)(q37.1; p16.2) translocation in the mother, suggesting a combination of 2q/4p trisomy/monosomy in all of the affected children of the family. Many private sporadic or recurrent MCA/MR syndromes maybe due to similar symmetric translocations, undetectable by conventional banding techniques.

Cerebral malformation, seizures, hypertrichosis, distinct face, claw hands, and overlapping fingers in sibs of both sexes

We report on sibs of both sexes with a multiple malformation syndrome of cerebral malformation, seizures, hypertrichosis, distinct face, claw hands, and overlapping fingers. The older boy died in a tonic extension spasm at age 4 months. When discharged, the younger girl was 3.5 months old. This appears to be an autosomal recessive syndrome which to our knowledge has not been described before.

A new recessive syndrome of unusual facies and multiple structural abnormalities

Two sibs with a similar pattern of dysmorphic facial features and multiple structural abnormalities are reported. Both had a normal karyotype. The parents are first cousins and neither shows any stigmata of the disorder. In view of the consanguinity and pattern of malformations, autosomal recessive inheritance seems likely.