Identical monochorionic twins with down syndrome and paternal origin of the extra chromosome 21.

UNLABELLED: Trisomy 21, the cause of Down syndrome (DS), is the most frequent trisomy in humans. The risk for DS increases with maternal age: mothers under 25 years of age are known to have an average risk of a DS pregnancy of 1: 1600, rising to 1: 350 at age 35 and to 1: 40 at 43, respectively. Twins with DS are rare. We report on monozygotic (MZ), monochorionic twin sisters with DS, whose parents are young (24 and 26 years old, respectively) and healthy. Family history is non contributory; pregnancy and delivery were uneventful. Both girls presented at birth with clinical manifestations of Down syndrome, that was confirmed cytogenetically (47XX,+21). Microsatellites analysis indicated that the twins are identical and that the extra chromosome 21 was of paternal origin. CONCLUSIONS: For practical purposes, the causative non disjunction should be considered a single sporadic event, with an empirical recurrence risk estimated at about 1%.

The Simpson-Golabi-Behmel syndrome: A clinical case and a detective story.

The Simpson-Golabi-Behmel syndrome (SGBS) is an overgrowth condition comprising "coarseness" of facial traits, supernumerary nipples, congenital heart defects, polydactyly and fingernail hypoplasia, and an increased risk of neonatal death and later neoplasia. Psychomotor development is usually normal. The syndrome is caused by mutation/deletion of the X-linked gene GPC3. We describe a new case of SGBS, that led to the discovery of an extended family segregating a GPC3 mutation and, ultimately, of an affected relative forgotten, but not lost, in an anatomical museum, where he was classified as a macrosomic newborn, who was born probably around 1940 and died neonatally of unknown cause. This baby boy becomes the oldest case of SGBS on record.

Cardio-facio-cutaneous syndrome: phenotypic variability and differential diagnosis in 3 cases with de novo BRAF mutations.

Cardio-facio-cutaneous (CFC) syndrome is a developmental disorder causing mental retardation and multiple congenital anomalies, including craniofacial, ectodermal, cardiac and musculoskeletal defects. Mutation of several genes in the RAS/MAPK (mitogen activated protein kinase) signaling pathway, most commonly BRAF, results in CFC syndrome. In this study, we report 3 new patients with CFC syndrome caused by mutation of BRAF. These patients differed in neurological impairment, craniofacial features and cardiac defects, while they shared relatively similar ectodermal and skeletal anomalies. They also displayed some overlapping features with Costello syndrome, another RAS/MAPK pathway disorder. Our findings highlight the clinical variability of CFC syndrome, with respect to severity and pattern of the affected organs, as well as the phenotypic overlap with the Costello syndrome.

A case of CMT 1B due to Val 102/fs null mutation of the MPZ gene presenting as hyperCKemia.

Charcot-Marie-Tooth disease (CMT) is a group of clinically and genetically heterogeneous neuropathies classically divided into demyelinating (CMT1) and axonal forms (CMT2). The most common demyelinating form is CMT1A, due to a duplication in the gene encoding the peripheral myelin protein 22 (PMP22). Less frequently, mutations in the myelin protein zero gene (MPZ/P0) account for demyelinating CMT1B. Herein, we report a patient presenting with an isolated hyperCKemia in whom electrophysiological and pathological findings revealed a demyelinating and axonal neuropathy. Sequencing of the MPZ gene revealed a 306delA at codon 102 in the proband and in two relatives. This mutation has been already described in association with paucisymptomatic CMT without hyperCKemia.

Assisted reproductive technology and congenital overgrowth: some speculations on a case of Pallister-Killian syndrome.

We report on a boy with Pallister-Killian syndrome (PKS) who was conceived by assisted reproductive technology (ART), specifically in vitro fertilization (IVF) with parents' gametes. A prenatal diagnosis performed elsewhere by CVS failed to detect the presence of the isochromosome 12p that was demonstrated postnatally in approximately 50% of cultured skin fibroblasts. Given that the patient did not show the congenital overgrowth typical of PKS, we speculate that ART might have restricted overgrowth in this particular case. More broadly, we hypothesize that overgrowth might protect from early demise fetuses conceived by ART, a technology known to cause low and very low birth weight.

Nonhomologous Robertsonian translocations (NHRTs) and uniparental disomy (UPD) risk: an Italian multicentric prenatal survey.

OBJECTIVES: The risk of uniparental disomy (UPD) occurrence associated with the prenatal finding of balanced nonhomologous Robertsonian translocations (NHRTs) has been estimated only on limited empirical data. The aim of the study was to verify the estimate of the general risk, to get narrower confidence intervals by cumulating the data and to obtain risk estimates for specific translocation types. METHODS: We tested for UPD 160 prenatal specimens referred to the participant centers after the cytogenetic finding of NHRT. RESULTS: One case of upd(14)mat was found, associated with a 45,XX,der(14;22)mat fetal karyotype. The general empirical risk of UPD occurrence in NHRT carrier fetuses, corrected for the actual number of chromosomes analyzed, was 0.76% (95% CI 0.02-4.25%). Cumulative data with previous studies gives a general risk of UPD associated with NHRT of 0.80% (95% CI 0.17-2.34%). The UPD risk for the specific NHRT der(13;14) did not significantly differ from that of the other NHRTs taken together. CONCLUSION: The present survey confirms the previously estimated risk of occurrence of UPD in offspring of NHRT carriers as a low, but not negligible risk, worth being investigated in prenatal diagnosis.

Concurrent lymph node metastases of medullary and papillary thyroid carcinoma in a case with RET oncogene germline mutation.

We report the case of a 72 yr-old woman who underwent total thyroidectomy and resection of neck lymph nodes because of a firm nodule in the right lobe, which was consistent with medullary thyroid carcinoma (MTC) on cytological examination. Histology showed multifocal bilateral MTC; a 2 mm papillary thyroid carcinoma (PTC) was also detected in the right lobe, next to a focus of MTC; five cervical lymph nodes contained MTC. In one right perithyroidal lymph node, concurrent metastases of MTC and PTC were demonstrated. DNA analysis showed a point mutation in exon 14 at codon 804 of the RET proto-oncogene locus, as frequently found in cases of familial MTC (FMTC). To our knowledge, this case represents the first documented case of concurrent lymph node metastases of MTC and PTC in a patient with RET proto-oncogene germline mutation. We report this unique case, discuss related thyroid malignancies, and suggest possible underlying pathogenetic mechanisms.

PTPN11 mutations are not responsible for the Cardiofaciocutaneous (CFC) syndrome.

Cardiofaciocutaneous (CFC) syndrome is a multiple congenital anomalies/mental retardation syndrome characterized by congenital heart defects, characteristic facial appearance, short stature, ectodermal abnormalities and mental retardation. It was described in 1986, and to date is of unknown genetic etiology. All reported cases are sporadic, born to non-consanguineous parents and have apparently normal chromosomes. Noonan and Costello syndromes remain its main differential diagnosis. The recent finding of PTPN11 missense mutations in 45-50% of the Noonan patients studied with penetrance of almost 100% and the fact that in animals mutations of this gene cause defects of semilunar valvulogenesis, made PTPN11 mutation screening in CFC patients a matter of interest. We sequenced the entire coding region of the PTPN11 gene in ten well-characterised CFC patients and found no base changes. We also studied PTPN11 cDNA in our patients and demonstrated that there are no interstitial deletions either. The genetic cause of CFC syndrome remains unknown, and PTPN11 can be reasonably excluded as a candidate gene for the CFC syndrome, which we regard as molecular evidence that CFC and Noonan syndromes are distinct genetic entities.

[L-acetylcarnitine treatment on fragile X patients hyperactive behaviour]. / El tratamiento con L-acetilcarnitina del comportamiento hiperactivo de pacientes con el síndrome X frágil.

Hyperactivity is a significant problem for almost all young males affected by fragile X syndrome (FXS), the most common inherited disease causing mental retardation. Therapeutical approaches are actually based on Central Nervous System (CNS) stimulants lacking a well defined rationale and efficacy while they further decrease the patient's limited attention span. A pilot study on 17 fragile X male treated with L-acetylcarnitine (LAC) over one year, showed a significant reduction of their hyperactivity behaviour tested by the Conners Abbreviated Parent-Teacher Questionnaire. LAC use in FXS patients derives from the hypothesis that the biochemical and physiological properties this substance has may preserve brain activity. LAC is a small, hydrosoluble molecule that easily diffuses in the extracellular space and enters any cell in the nervous system through specific transporters. Different cerebral areas use this molecule differently to metabolize glucose and lipids to provide for ATP and neurotrasmitters synthesis. The acetyl group LAC carriers represents a key metabolic signaling element possibly mediating its effect in the CNS. The exogenous administration of LAC may affect brain activity in FXS by: I) modulation of fuel partitioning for energy production, which at the mithocondrial level is associated with the Kreb's cycle metabolic role in neurotransmitter synthesis; II) remodelling of lipid membrane in terms of LAC actively determining the production of polyunsaturated fatty acids; III) preferential effect on the attention component of the cholinergic system which relies on its peculiar modality of communication in the CNS. Based on the above premises an explorative, double-blind, placebo controlled, multicenter study is ongoing. A total population of 160 children from nine European centers will be enrolled. The objective of this study is to determine the effect of LAC on the hyperactive behaviour of FXS children as evaluated by the administration of the Conners Abbreviated Parent Questionnaire.

Synergistic effect of histone hyperacetylation and DNA demethylation in the reactivation of the FMR1 gene.

Most fragile X syndrome patients have expansion of a (CGG)(n)sequence with >200 repeats (full mutation) in the FMR1 gene responsible for this condition. Hypermethylation of the expanded repeat and of the FMR1 promoter is almost always present and apparently suppresses transcription, resulting in absence of the FMR1 protein. We recently showed that transcriptional reactivation of FMR1 full mutations can be achieved by inducing DNA demethylation with 5-azadeoxycytidine (5-azadC). The level of histone acetylation is another important factor in regulating gene expression; therefore, we treated lymphoblastoid cell lines of non-mosaic full mutation patients with three drugs capable of inducing histone hyperacetylation. We observed a consistent, although modest, reactivation of the FMR1 gene with 4-phenylbutyrate, sodium butyrate and trichostatin A, as shown by RT-PCR. However, we report that combining these drugs with 5-azadC results in a 2- to 5-fold increase in FMR1 mRNA levels obtained with 5-azadC alone, thus showing a marked synergistic effect of histone hyperacetylation and DNA demethylation in the reactivation of FMR1 full mutations.

Mosaicism for the full mutation and a microdeletion involving the CGG repeat and flanking sequences in the FMR1 gene in eight fragile X patients.

The molecular mechanism of the fragile X syndrome is based on the expansion of an unstable CGG repeat in the 5' untranslated region of the FMR1 gene in most patients. This expansion is associated with an abnormal DNA methylation leading to the absence of production of FMR1 protein (FMRP). Such expansion apparently predisposes the repeat and flanking regions to further instability that may lead to mosaic conditions with a full mutation and a premutation or, rarely, with normal or reduced alleles that can sometimes be transcriptionally active. In this study we describe eight unrelated fragile X patients who are mosaic for both a full mutation and an allele of normal (four cases) or reduced size (four cases). Sequencing analysis of the deletion breakpoints in 6 patients demonstrated an internal deletion confined to the CGG repeat in four of them, which represents the most likely explanation for the regression of the full mutation to a normal sized allele. In two patients with a reduced allele, the deletion encompassed the entire CGG repeat and part of the flanking regions. Analysis of FMRP by Western blot was performed in one of the mosaics with a normal sized allele and in three of those with a reduced allele. In the first patient's lymphocytes FMRP was detected, whereas in the three other patients the deletion is likely to impair transcription as no FMRP was present in their lymphocytes.

Mosaic trisomy 17 in amniocytes: phenotypic outcome, tissue distribution, and uniparental disomy studies.

Mosaicism for trisomy 17 in amniocyte cultures is a rare finding, whilst postnatal cases are exceptional. In order to gain insight into the possible effects of the distribution of the trisomic line and of uniparental disomy (UPD) on embryofoetal development, we have performed follow-up clinical, cytogenetic and molecular investigations into three newly detected prenatal cases of trisomy 17 mosaicism identified in cultured amniotic fluid. In the first case, the pregnancy ended normally with the birth of a healthy girl, and analysis of newborn lymphocytes and of multiple extra-embryonic tissues was indicative of confined placental mosaicism. The second case was also associated with a normal pregnancy outcome and postnatal development, and only euploid cells were found in peripheral blood after birth. However, maternal isodisomy 17 consequent to a meiosis II error and loss of a chromosome 17 homologue was detected in peripheral lymphocytes postnatally. In the third case, pathological examination after termination of pregnancy showed growth retardation and minor dysmorphisms, and the trisomic line was detected in foetal skin fibroblasts. In addition, biparental derivation of chromosome 17 was demonstrated in the euploid lineage. These results, together with previously reported data, indicate that true amniotic trisomy 17 mosaicism is more commonly of extra-embryonic origin and associated with normal foetal development. Phenotypic consequences may arise when the trisomic line is present in foetal tissues. Case 2 also represents the first observation of maternal UPD involving chromosome 17; the absence of phenotypic anomalies in the child suggests that chromosome 17 is not likely to be subject to imprinting in maternal gametes.

In vitro reactivation of the FMR1 gene involved in fragile X syndrome.

Fragile X syndrome is the most frequent cause of heritable mental retardation. Most patients have a mutation in the 5' untranslated region of the FMR1 gene, consisting of the amplification of a polymorphic (CGG)nrepeat sequence, and cytogenetically express the folate-sensitive fragile site FRAXA in Xq27.3. Fragile X patients harbour an expanded sequence with >200 CGG repeats (full mutation), accompanied by methylation of most cytosines of the sequence itself and of the upstream CpG island. This abnormal hypermethylation of the promoter suppresses gene transcription, resulting in the absence of the FMR1 protein. Rare individuals of normal intelligence were shown to carry a completely or partially unmethylated full mutation and to express the FMR1 protein. Given this observation and knowing that the open reading frame of the mutated FMR1 gene is intact, we decided to investigate whether its activity could be restored in vitro by inducing DNA demethylation with 5-azadeoxycytidine (5-azadC) in fragile X patients' lymphoblastoid cells. We report that treatment with 5-azadC causes reactivation of fully mutated FMR1 genes with 300-800 repeats, as shown by the restoration of specific mRNA and protein production. This effect correlates with the extent of promoter demethylation, determined by restriction analysis with methylation-sensitive enzymes. These results confirm the critical role of FMR1 promoter hypermethylation in the pathogenesis of the fragile X syndrome, provide an additional explanation for the normal IQ of the rare males with unmethylated full mutations and pave the way to future attempts at pharmacologically restoring mutant FMR1 gene activity in vivo.

The inv dup(15) syndrome: a clinically recognizable syndrome with altered behavior, mental retardation, and epilepsy.

The most common of the heterogeneous group of the extra structurally abnormal chromosomes (ESACs) is the inv dup(15), whose presence results in tetrasomy 15p and partial tetrasomy 15q. Inv dup(15), containing the Prader-Willi/Angelman syndrome (PWS/AS) region, are constantly associated with phenotypic abnormalities and mental retardation. We report on four additional patients with inv dup(15), whose behavioral pattern, and neurologic and physical findings further delineate the phenotype of this neurogenetic syndrome. We also provide FISH analyses on chromosomes of the observed ESACs and discuss the role of a number of genes located within the tetrasomic region.

Characterization of MSH2 and MLH1 mutations in Italian families with hereditary nonpolyposis colorectal cancer.

Mismatch repair genes MSH2 and MLH1 are considered to be the two major genes that are responsible for hereditary nonpolyposis colorectal cancer (HNPCC). Germline heterozygous inactivating mutations of MSH2 and MLH1 have been identified previously in a substantial fraction of individuals who are predisposed genetically to colorectal carcinoma (CRC) and other tumors of the HNPCC spectrum. With the aim of determining the relevance of these two genes in the Italian population, we submitted to mutational analysis a set of 17 HNPCC families, all of which fulfilled the "Amsterdam criteria." A combination of different techniques, including reverse transcription-polymerase chain reaction (RT-PCR) of long fragments and single-strand conformation polymorphism (SSCP) on cDNA and genomic DNA, allowed the identification of ten molecular variants, seven of which are predicted to inactivate mismatch repair function. The mutated predisposing gene was MSH2 in two families and MLH1 in five other families. All of the mutations were characterized by DNA sequencing and appeared to involve different molecular mechanisms, such as short in-frame and out-of-frame deletions, splicing errors, and nonsense mutations. This study also demonstrates that, in the Italian population, a considerable fraction of HNPCC families (at least 41%) is linked to MSH2 and MLH1 mutations.

Clinical case report: multiple idiosyncratic adverse effects of antiepileptic drugs in trisomy 9p.

We report the case of a mentally retarded 30 y.o. patient with partial trisomy of chromosome 9, affected by epilepsy. Following treatment with antiepileptic drugs (AEDs), the patient developed several rare complications: after beginning therapy with phenytoin, the patient developed pseudolymphoma; after monotherapy with carbamazepine (CBZ), the patient thereafter developed myoclonic jerks of upper and lower limbs upon awakening; after one year of treatment with valproate (VPA) the patient developed clinical and immuno-haematological signs of SLE. Gradual withdrawal of AED, obtained clinical remission. The possibility that the chromosomal abnormality of the patient was responsible for the three rare complications observed during AED therapy is considered.

Molecular and cytogenetic characterization of a recurrent unbalanced translocation (4;21)(p16.3;q22.1): relevance to the Wolf-Hirschhorn and Down syndrome critical regions.

We report on an aneuploidy syndrome due to the unbalanced segregation of a familial translocation (4;21)(p16.3;q22.1) causing a partial 4p monosomy and a partial 21q trisomy. The three affected children presented with severe failure to thrive, short stature, microcephaly, profound hypotonia, and mental retardation. The face, very similar in the three children, is characterized by frontal bossing, upslanting of the palpebral fissures, short nose, and deep set ears, giving the overall appearance of the Down syndrome. The molecular study has defined the aneuploid segment on both 4p and 21q. Most of the Down syndrome critical region was found to the trisomic, while only part of the candidate Wolf-Hirschhorn syndrome critical region was deleted, suggesting that this region is not critical for the major malformations characteristic for WHS.