Clinical and genetic analysis of a child with maternal uniparental disomy of chromosome 20 / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical and genetic characteristics of a boy with isolated maternal uniparental disomy of chromosome 20 [UPD(20)mat].@*METHODS@#A child who was admitted to the Tongji Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology on April 8,2021. was selected as the study subject. Phenotypic and endocrinological findings of the child were retrospectively analyzed. Whole exome sequencing (WES) and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) were carried out for detecting the UPD sequences and copy number variations. Both of his parents were verified by Sanger sequencing. Relevant literature was systematically reviewed.@*RESULTS@#The child, a 3-year-and-8-month-old boy born to a 41-year-old mother by Cesarean delivery at 36+2 gestational weeks due to oligohydramia, had a birth weight of 2 300 g and length of 46 cm. He was admitted to the NICU for feeding difficulties which had persisted despite of clinical management. At the age of 3.75, he had a height of 92.5 cm (< 3rd percentile; 25th ~ 50th percentile at 2.5 years) and a weight of 10.8 kg (< 3rd percentile; 50th percentile at 15 months). He had also presented with growth retardation, short stature, attention deficit and hyperactivity disorder (ADHD), mild mental retardation, and speech and language development disorders. He had simian creases in both hands but no additional dysmorphic signs, and his motor development was normal. Serum insulin, thyroid-stimulating hormone, and insulin growth factor binding protein 3 levels were within the normal ranges, though insulin growth factor-1 (IGF-1) was slightly decreased. Since that time he had continuously used atomoxetine hydrochloride capsules to control his ADHD. WES and MS-MLPA revealed the existence of UPD (20)mat.@*CONCLUSION@#The UPD(20)mat syndrome is characterized by feeding difficulties, growth retardation and short stature. The child in our case has been accompanied by ADHD and speech and language development disorders, which required long-term treatment. For women with advanced maternal age and suggestive phenotypes, genetic testing and counseling should be conducted.

Study of a fetus with confined placental mosaicism for trisomy 2 in conjunct with fetal uniparental disomy and a literature review / 中华医学遗传学杂志

OBJECTIVE@#To carry out genetic analysis for a fetus with confined placental mosaicism (CPM) for trisomy 2 (T2) in conjunct with fetal uniparental disomy (UPD).@*METHODS@#Amniocentesis and chromosomal karyotyping was carried out for a pregnant woman with a high risk for chromosome 2 anomalies indicated by non-invasive prenatal testing (NIPT). Single nucleotide polymorphism array (SNP-array) and trio-whole exome sequencing (Trio-WES) were carried out. Ultrasonography was used to closely monitor the fetal growth. Multifocal sampling of the placenta was performed after delivery for copy number variation sequencing (CNV-seq).@*RESULTS@#The fetus was found to have a normal chromosomal karyotype. SNP-array has revealed multiple regions with loss of heterozygosity (LOH) on chromosome 2. Trio-WES confirmed the presence of maternal UPD for chromosome 2. Ultrasonography has revealed intrauterine growth restriction and oligohydramnios. Intrauterine fetal demise had occurred at 23+4 weeks of gestation. Pathological examination had failed to find salient visceral abnormality. The placenta was proved to contain complete T2 by CNV-seq.@*CONCLUSION@#T2 CPM can cause false positive result for NIPT and may be complicated with fetal UPD, leading to adverse obstetric outcomes such as intrauterine growth restriction, oligohydramnios and intrauterine fetal demise.

Clinical practice guidelines for the diagnosis of regions of homozygosity and uniparental disomy / 中华医学遗传学杂志

The overall prevalence of uniparental disomy (UPD) across all chromosomes was estimated to be around one birth in 2000. To date, more than 4170 UPD cases have been registered. UPD for chromosomes 6, 7, 11, 14, 15, and 20 can result in clinically recognizable imprinting disorders due to abnormal levels of imprinted gene expression. For other chromosomes, the clinical consequences associated with UPD are not apparent, unless when a recessive genetic disorder is unmasked by UPD or regions of homozygosity (ROH). A clinical practice guideline will assist in strengthening the precise analysis and interpretation of the clinical significance of ROH/UPD. This guideline summarizes the conception, mechanism and clinical consequences of ROH/UPD, as well as the principles for data analysis, with an aim to standardize the clinical application and data interpretation.

Clinical practice guidelines for the diagnosis of regions of homozygosity and uniparental disomy / 中华医学遗传学杂志

The overall prevalence of uniparental disomy (UPD) across all chromosomes was estimated to be around one birth in 2000. To date, more than 4170 UPD cases have been registered. UPD for chromosomes 6, 7, 11, 14, 15, and 20 can result in clinically recognizable imprinting disorders due to abnormal levels of imprinted gene expression. For other chromosomes, the clinical consequences associated with UPD are not apparent, unless when a recessive genetic disorder is unmasked by UPD or regions of homozygosity (ROH). A clinical practice guideline will assist in strengthening the precise analysis and interpretation of the clinical significance of ROH/UPD. This guideline summarizes the conception, mechanism and clinical consequences of ROH/UPD, as well as the principles for data analysis, with an aim to standardize the clinical application and data interpretation.

Adrenal Cortical Neoplasm with Uncertain Malignant Potential Arising in the Heterotopic Adrenal Cortex in the Liver of a Patient with Beckwith-Wiedemann Syndrome

Patients with Beckwith-Wiedemann syndrome (BWS) are predisposed to developing embryonal tumors, with hepatoblastoma being the most common type. Our patient showed hemihypertrophy, macroglossia, and paternal uniparental disomy in chromosome 11 and was diagnosed with BWS. When the patient was 9 months old, a 2.5×1.5 cm oval hypoechoic exophytic mass was detected in the inferior tip of his right liver. Preoperative imaging identified it as hepatoblastoma; however, histologic, immunohistochemistry, and electron microscopic findings were compatible with adrenal cortical neoplasm with uncertain malignant potential. The origin of the adrenal tissue seemed to be heterotopic. Here, we describe for the first time an adrenal cortical neoplasm with uncertain malignant potential arising in the heterotopic adrenal cortex located in the liver of a patient with BWS.

Research progress on uniparental disomy in cancer / 浙江大学学报·医学版

Uniparental disomy (UPD) refers to a chromosome defect that an individual's homologous chromosome or segments are inherited from one parent. UPD can cause either aberrant patterns of genomic imprinting or homozygosity of mutations, leading to various diseases, including cancer. The mechanisms of UPD formation are diverse but largely due to the incorrect chromosome separation during cell division. UPD does not alter the number of gene copies, thus is difficult to be detected by conventional cytogenetic techniques effectively. Assisted by the new techniques such as single nucleotide polymorphism arrays, more and more UPD-related cases have been reported recently. UPD events are non-randomly distributed across cancer types, which play important role in the occurrence, development and metastasis of cancer. Here we review the research progress on the formation mechanisms, detection methods, the involved chromosomal regions and genes, and clinical significance of UPD; and also discuss the directions for future studies in this field.

Influence of uniparental disomy on the conclusion of paternity testing / 中华医学遗传学杂志

OBJECTIVE@#To explore the influence of uniparental disomy (UPD) on bipartite and tripartite paternity testing.@*METHODS@#Two cases of paternity testing were analyzed by multiplex amplification and capillary electrophoresis typing. Suspected UPD was verified by using single nucleotide polymorphism array (SNP array). Parental power index was calculated by using a bipartite or tripartite model.@*RESULTS@#The two cases were found to harbor respectively three short tandem repeats on chromosome 2 and two short tandem repeats on chromosome 15. SNP array verified that both cases were of UPD. Case 1 had a parental power index of 122274987565.23 by a tripartite model, while case 2 had a parental power index of 13500.8463 by a bipartite model. Based on the technical specification, the conclusions supported a biological parent-child relationship in both cases.@*CONCLUSION@#UPD may lead to misjudgment of paternity testing. The possibility of UPD should be considered when certain loci which do not conform to Mendelian inheritance have aggregated to one chromosome.

Genetic analysis of an adult with mosaicism of uniparental disomy 11p / 中华医学遗传学杂志

OBJECTIVE@#To analyze the clinical phenotype and genomic abnormality of an adult featuring congenital heart defect and multiple developmental disorders.@*METHODS@#The patient was subjected to conventional G-banding chromosomal karyotyping and single nucleotide polymorphism microarray (SNP-array) analysis.@*RESULTS@#The patient showed a normal karyotype, while SNP-array revealed a 42.7 Mb mosaic uniparental disomy (UPD) in the 11p15.5p12 region ([hg19] chr11: 491 333-43 189 376).@*CONCLUSION@#The mosaicism of UPD of 11p15.5p12 region probably underlies the congenital heart defect and developmental disorders in the patient.

Análisis de variación del número de copias y de patrones de metilación en la región 15q11-q13 / Variation analysis of the number of copies and methylene patterns in region 15q11-q13

La región q11-q13 del cromosoma 15 humano es proclive a sufrir alteraciones genéticas. Algunos genes de la región presentan expresión parental diferencial monoalélica, regulada por imprinting (EI). Errores en la regulación del EI, disomías uniparentales (DSU), así como también el cambio en el número de copias genómicas (CNV) producidos por sitios susceptibles de quiebre cromosómico (BP), producen alteraciones en esta región. Las enfermedades más frecuentes asociadas son el síndrome de Prader-Willi, el síndrome de Angelman y el síndrome de microduplicación 15q11-q13. En el presente trabajo analizamos la región 15q11-q13 por Methyl specific-multiplex ligation-dependent probe amplification (MS-MLPA) en 181 muestras de ADN derivadas a nuestro servicio de análisis genético molecular. En este trabajo mostramos que, de las 181 muestras, 39 presentaron alteraciones detectables por MS-MLPA. El 61.5% (24/39) de esas alteraciones detectadas fueron deleciones, el 5.1% (2/39) duplicaciones y el 33.3%(13/39) DSU/EI. Los CNV fueron 4 veces más frecuentes que las DSU/EI (OR = 4; IC 95%: 1.56-10.25) consistente con la literatura. Entre los CNV, dos casos atípicos permiten postular posibles sitios BP que no han sido informados en la literatura previamente.

Human chromosome 15q11-q13 region is prone to suffer genetic alterations. Some genes of this region have a differential monoallelic imprinting-regulated expression pattern. Defects in imprinting regulation (IE), uniparental disomy (UPD) or copy number variation (CNV) due to chromosomal breakpoints (BP) in 15q11-q13 region, are associated with several diseases. The most frequent are Prader-Willi syndrome, Angelman syndrome and 15q11-q13 microduplication syndrome. In this work, we analyzed DNA samples from 181 patients with phenotypes which were compatible with the above-mentioned diseases, using Methyl specific-multiplex ligation-dependent probe amplification (MS-MLPA). We show that, of the 181 samples, 39 presented alterations detectable by MS-MLPA. Of those alterations, 61.5% (24/39) were deletions, 5.1% (2/39) duplications and 33.3% (13/39) UPD/IE. The CNV cases were 4 times more frequent than UPD/IE (OR= 4; IC 95%: 1.56-10.25), consistent with the literature. Among the CNVs, two atypical cases allow to postulate new possible BP sites that have not been reported previously in the literature.

A Unique Mutational Spectrum of MLC1 in Korean Patients With Megalencephalic Leukoencephalopathy With Subcortical Cysts: p.Ala275Asp Founder Mutation and Maternal Uniparental Disomy of Chromosome 22

BACKGROUND: Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare inherited disorder characterized by infantile-onset macrocephaly, slow neurologic deterioration, and seizures. Mutations in the causative gene, MLC1, are found in approximately 75% of patients and are inherited in an autosomal recessive manner. We analyzed MLC1 mutations in five unrelated Korean patients with MLC. METHODS: Direct Sanger sequencing was used to identify MLC1 mutations. A founder effect of the p.Ala275Asp variant was demonstrated by haplotype analysis using single-nucleotide polymorphic (SNP) markers. Multiple ligation-dependent probe amplification (MLPA) and comparative genomic hybridization plus SNP array were used to detect exonic deletions or uniparental disomy (UPD). RESULTS: The most prevalent pathogenic variant was c.824C>A (p.Ala275Asp) found in 7/10 (70%) alleles. Two pathogenic frameshift variants were found: c.135delC (p.Cys46Alafs*12) and c.337_353delinsG (p.Ile113Glyfs*4). Haplotype analysis suggested that the Korean patients with MLC harbored a founder mutation in p.Ala275Asp. The p.(Ile113Glyfs*4) was identified in a homozygous state, and a family study revealed that only the mother was heterozygous for this variant. Further analysis of MLPA and SNP arrays for this patient demonstrated loss of heterozygosity of chromosome 22 without any deletion, indicating UPD. The maternal origin of both chromosomes 22 was demonstrated by haplotype analysis. CONCLUSIONS: This study is the first to describe the mutational spectrum of Korean patients with MLC, demonstrating a founder effect of the p.Ala275Asp variant. This study also broadens our understanding of the mutational spectrum of MLC1 by demonstrating a homozygous p.(Ile113Glyfs*4) variant resulting from UPD of chromosome 22.

A case of maternal uniparental disomy of chromosome 20 detected by noninvasive prenatal test of 1,000 high-risk pregnancies

Chromosomal loss in trisomy (trisomy rescue) to generate a disomic fetus can cause confined placental mosaicism and/or feto/placental mosaicism. After trisomy rescue event, there is a risk of fetal uniparental disomy (UPD). Noninvasive prenatal test (NIPT) reflects the genomic constitution of the placenta, not of the fetus itself. Feto-placental discrepancy can therefore cause false-positive (trisomy) NIPT results. These discordant NIPT results can serve as important clues to find UPD associated with confined placental mosaicism. We report a case with maternal UPD of chromosome 20, detected by NIPT of 1,000 high-risk pregnancies, carried out for detecting chromosomal abnormalities in Koreans.

Pseudohypoparathyroidism type 1b due to paternal uniparental disomy of chromosome 20q: A case report

Pseudohypoparathyroidism type 1b (PHP 1b) is the result of end organ resistance to parathyroid hormone (PTH) in the absence of any features of Albright's hereditary osteodystrophy. There are two subtypes of PHP 1b with different genetic mechanisms. One subtype is related to a maternally derived 3kb microdeletion involving STX 16 gene, and is inherited in an autosomal dominant mode. Familial autosomal dominant inheritance of PHP 1b is relatively rare. The other subtype is associated with more extensive loss of imprinting at the GNAS locus that affects at least one additional differential methylated (hypermethylation at neuroendocrine secretory protein and hypomethylation at antisense transcript and or extra-large stimulatory G protein region) without microdeletion of the STX 16 or AS gene. It can be sporadic due to an imprinting defect in the GNAS gene. In our case, an 8-year-old girl was referred for suspected PHP with no feature of Albright hereditary osteodystrophy. Blood test results revealed hypocalcemia and hyperphosphatemia. Elevated PTH was also checked. There was no family history of endocrine or developmental problem. Her intelligence was normal, but she had inferior sociability at that time. Based on above, we diagnosed a rare case of paternal uniparental disomy of the long arm of chromosome 20 as the cause of PHP 1b by microsatellite marker test of chromosome 20.

A boy with Meier-Gorlin syndrome carrying a novel ORC6 mutation and uniparental disomy of chromosome 16 / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify the genetic cause for a 11-year-old Chinese boy with Meier-Gorlin syndrome (MGS).</p><p><b>METHODS</b>Chromosomal microarray analysis (CMA) was used to detect potential variations, while whole exome sequencing (WES) was used to identify sequence variants. Sanger sequencing was used to confirm the suspected variants.</p><p><b>RESULTS</b>The boy has featured short stature, microtia, small patella, slender body build, craniofacial anomalies, and small testes with normal gonadotropin. A complete uniparental disomy of chromosome 16 was revealed by CMA. WES has identified a novel homozygous mutation c.67A>G (p.Lys23Glu) in ORC6 gene mapped to chromosome 16. As predicted by Alamut functional software, the mutation may affect the function of structural domain of the ORC6 protein.</p><p><b>CONCLUSION</b>The patient is probably the first diagnosed MGS case in China, who carried a novel homozygous mutation of the ORC6 gene and uniparental disomy of chromosome 16. The effect of this novel mutation on the growth and development needs to be further investigated.</p>

Birth seasonality in Korean Prader-Willi syndrome with chromosome 15 microdeletion

PURPOSE: Prader-Willi syndrome (PWS) is a well-known genetic disorder, and microdeletion on chromosome 15 is the most common causal mechanism. Several previous studies have suggested that various environmental factors might be related to the pathogenesis of microdeletion in PWS. In this study, we investigated birth seasonality in Korean PWS. METHODS: A total of 211 PWS patients born from 1980 to 2014 were diagnosed by methylation polymerase chain reaction at Samsung Medical Center. Of the 211 patients, 138 were born from 2000-2013. Among them, the 74 patients of a deletion group and the 22 patients of a maternal uniparental disomy (UPD) group were compared with general populations born from 2000 using the Walter and Elwood method and cosinor analysis. RESULTS: There was no statistical significance in seasonal variation in births of the total 211 patients with PWS (chi2=7.2522, P=0.2982). However, a significant difference was found in the monthly variation between PWS with the deletion group and the at-risk general population (P<0.05). In the cosinor model, the peak month of birth for PWS patients in the deletion group was January, while the nadir occurred in July, with statistical significance (amplitude=0.23, phase=1.2, low point=7.2). The UPD group showed the peak birth month in spring; however, this result was not statistically significant (chi2=3.39, P=0.1836). CONCLUSION: Correlation with birth seasonality was identified in a deletion group of Korean PWS patients. Further studies are required to identify the mechanism related to seasonal effects of environmental factors on microdeletion on chromosome 15.

Application of chromosome microarray analysis for prenatal diagnosis of a fetus with partial duplication of 1p and uniparental disomy of chromosome 6 / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the genetic cause for a fetus with structural anomaly, and to correlate the phenotype with the genotype.</p><p><b>METHODS</b>Amniotic fluid was obtained following the revelation of structural anomaly by ultrasonography. Cell culture and direct DNA extraction were performed in parallel. G-banded karyotyping analysis and chromosome microarray analysis (CMA) were subsequently carried out.</p><p><b>RESULTS</b>G-banded karyotyping has suggested the fetus to be a normal male. However, CMA analysis has revealed the presence of a mosaic 3.24 Mb duplication of 1p36.33p36.32 (24%) and uniparental disomy (UPD) of chromosome 6. The genetic diagnosis for the fetus was therefore 46,XY, arr 1p36.33 p36.32(849,466-4,090,472)×2-3, (6)×2 hmz. The anomaly can probably explain the ultrasound findings in the fetus.</p><p><b>CONCLUSION</b>Compared with conventional cytogenetic methods, CMA has greater resolution and throughput, and can serve as a more efficient platform for the detection of chromosomal microdeletion, microduplication, loss of heterozygosity and UPD.</p>

Unexpected Inheritance of a Balanced Homologous translocation t(22q;22q) from father to a phenotypically normal daughter.

Rearrangements between homologous chromosomes are extremely rare and manifest mainly as monosomic or trisomic offsprings. There are remarkably few reports of balanced homologous chromosomal translocation t (22q; 22q) and only two cases of transmission of this balanced homohologous rearrangement from mother to normal daughter are reported. Robersonian translocation carriers in non‑homologous chromosomes have the ability to have an unaffected child. However, it is not possible to have an unaffected child in cases with Robersonian translocations in homologous chromosomes. Carriers of homologous chromosome 22 translocations with maternal uniparental disomy do not have any impact on their phenotype. We are presenting a family with a history of multiple first trimester miscarriages and an unexpected inheritance of balanced homologous translocation of chromosome 22 with paternal uniparental disomy. There are no data available regarding the impact of paternal UPD 22 on the phenotype. We claim this to be the first report explaining that paternal UPD 22 does not impact the phenotype.

Pattern of chromosome involvement in childhood hyperdiploid pre-B-cell acute lymhoblastic leukemia cases from India.

BACKGROUND: Hyperdiploid pre‑B‑cell acute lymhoblastic leukemia (pre‑B‑ALL) is a common form of childhood leukemia with very good prognosis with present day chemotherapy. However, the chromosomal composition of the hyperdiploidy has not been extensively studied and possible mechanism for this pathology remains so far conjectural. OBJECTIVE: To analyze the pattern of chromosome involvement in a cohort of childhood hyperdiploid pre‑B‑ALL from India and from this pattern to develop an understanding on the causation of such pathology. Whether such patients also carry translocations and FLT3 mutations in addition to their hyperdiploid karyotype. MATERIALS AND METHODS: One hundred and twenty‑six childhood pre‑B‑ALL patients were studied. Bone marrow aspirate of these patients were evacuated for morphology, FAB classification, immunophenotyping and both conventional and molecular cytogenetics. RESULTS: Of 126 patients with pre‑B‑ALL (age 2-15 years), 90 patients with abnormal karyotype showed 50 with hyperdiploid karyotype (50/90 i.e. 55.5%). Chromosomes 9, 10, 14, 17, 18, 20 and 21 were more often involved in hyperdiploidy. Chromosome 21 duplication was present in 92% of the cases. Chromosomes 5, 15, 16, 17 and Y were less often involved (18-20%) in hyperdiploidy. About 44% of patients with hyperdiploidy had additional karyotypic abnormality of which TEL‑AML1 was predominant (24%). Chromosome loss was rare and accounted for 20% of the cases only. We did not find any FLT3 mutation in our patients. CONCLUSION: In this study, the pattern of chromosome involvement in hyperdiploid karyotype of ALL patients is same as other studies except some chromosomes like 1, 6, 11, 12, 19 and 22 have some more frequent involvement than other studies. This study also showed the occurrence of TEL/AML1 fusion is more (19.8%) than other reports from India.

Detection of mosaic trisomy 9 missed by conventional cytogenetics using SNP-array and fluorescence in situ hybridization / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect mosaic trisomy 9 missed by conventional cytogenetics.</p><p><b>METHODS</b>Peripheral blood genomic DNA from a girl with mental retardation was analyzed using Affymetrix CytoScan (TM) HD array. Fluorescence in situ hybridization (FISH) was also performed on samples from two patients.</p><p><b>RESULTS</b>The SNP-array analysis has revealed multiple duplications along chromosome 9. FISH analysis showed that, for the peripheral blood sample from one patient, 40 of 100 interphase cells and 15 of 100 metaphase cells carried trisomy 9. For the cord blood sample from another patient, 35 of 100 interphase cells and 10 of 100 cultured cells carried trisomy 9.</p><p><b>CONCLUSION</b>SNP-array is useful for detecting low-level mosaicism which may be missed by conventional cytogenetics. Combined with karyotype and microarray analyses, FISH is a focused and targeted approach for diagnosing mosaic trisomy. They may provide a useful tool for differentiating pseudomosaicisms from true mosaicisms.</p>

Phenotypic spectrum in uniparental disomy: Low incidence or lack of study.

CONTEXT: Alterations in the human chromosomal complement are expressed phenotypically ranging from (i) normal, via (ii) frequent fetal loss in otherwise normal person, to (iii) sub‑clinical to severe mental retardation and dysmorphism in live births. A subtle and microscopically undetectable chromosomal alteration is uniparental disomy (UPD), which is known to be associated with distinct birth defects as per the chromosome involved and parental origin. UPD can be evident due to imprinted genes and/or activation of recessive mutations. AIMS: The present study comprises of data mining of published UPD cases with a focus on associated phenotypes. The goal was to identify non‑random and recurrent associations between UPD and various genetic conditions, which can possibly indicate the presence of new imprinted genes. SETTINGS AND DESIGN: Data mining was carried out using the homepage “http://www.fish.uniklinikum‑jena.de/ UPD.html,” an online catalog of published cases with UPD. MATERIALS AND METHODS: The UPD cases having normal karyotype and with or without clinical findings were selected to analyze the associated phenotypes for each chromosome, maternal or paternal involved in UPD. RESULTS: Our results revealed many genetic conditions (other than the known UPD syndromes) to be associated with UPD. Even in cases of bad obstetric history as well as normal individuals chance detection of UPD has been reported. CONCLUSIONS: The role of UPD in human genetic disorders needs to be studied by involving larger cohorts of individuals with birth defects as well as normal population. The genetic conditions were scrutinized in terms of inheritance patterns; majority of these were autosomal recessive indicating the role of UPD as an underlying mechanism.

Another small supernumerary marker chromosome derived from chromosome 9 in a Klinefelter patient / Otro cromosoma marcador supernumerario pequeño derivado del cromosoma 9 en un paciente con el síndrome de Klinefelter

Marker chromosomes are very rare in Klinefelter patients and phenotypic findings are related to the affected chromosomal region. The phenotypic effects of small supernumerary marker chromosomes (sSMC) range from multiple malformations/mental retardation to no effect (ie a normal phenotype). This wide spectrum of phenotypes is due to the origin, structure and gene content of the marker chromosome. The first Klinefelter case with sSMC 9 was published by Liehr et al in 2005. The present case was referred for chromosomal analysis because of dysmorphic features, speech delay and mild mental retardation. Conventional cytogenetic analysis revealed the 47 XXY karyotype in 17 metaphases and the 48 XXY + marker karyotype in eight metaphases. Fluorescence in situ hybridization (FISH) analysis to identify the marker chromosome was performed using the LSI p16 (9p21) Spectrum Orange/CEP 9 SpectrumGreen Probe (Vysis CDKN2A/CEP 9 FISH Probe) and partial trisomy 9 mosaicism was confirmed in this patient. To our knowledge, this is the second case of Klinefelter syndrome with a small supernumerary marker chromosome derived from chromosome 9.

Los cromosomas marcadores son muy raros en los pacientes de Klinefelter, y los hallazgos fenotípicos se relacionan con la región cromosomática afectada. Los efectos fenotípicos de los cromosomas marcadores supernumerarios pequeños (sSMC) van desde el retraso mental y las malformaciones múltiples hasta la ausencia total de efectos (es decir, un fenotipo normal). Este amplio espectro de fenotipos se debe al origen, estructura y contenido del gen del cromosoma marcador. El primer caso de síntoma Klinefelter con sSMC 9 fue publicado por Liehr et al en 2005. El caso presente fue remitido para análisis cromosomático debido a rasgos dismórficos, retraso del habla, y retardo mental ligero. El análisis citogenético convencional reveló el cariotipo 47 XXY en 17 metafases y el cariotipo marcador 48 XXY+ en ocho metafases. El análisis mediante hibridación fluorescente in situ (FISH) para identificar el cromosoma marcador se realizó usando la sonda LSI p16 (9p21) Spectrum Orange/CEP 9 SpectrumGreen Probe (Vysis CDKN2A/CEP 9 FISH Probe). Un mosaicismo de trisomía 9 parcial fue confirmado en este paciente. Hasta donde sabemos, éste es el segundo caso de síndrome de Klinefelter con un cromosoma marcador supernumerario pequeño derivado del cromosoma 9.