Recomendaciones para el uso de microarrays en el diagnóstico prenatal / Recommendations for the use of microarrays in prenatal diagnosis

La tecnología de microarrays, de reciente implantación en el diagnóstico prenatal internacional, se ha convertido en uno de los pilares de este diagnóstico en cuanto a su capacidad de detección y objetividad de resultados. La presente guía comprende una exposición general de la tecnología, incluyendo aspectos técnicos y diagnósticos a tener en cuenta. En concreto, se definen: los distintos tipos de muestras prenatales que se van a utilizar (biopsia de vellosidades coriónicas, líquido amniótico, sangre procedente de cordón umbilical o material procedente de restos abortivos) así como las particularidades de cada una de ellas; qué puntos hay que tener en cuenta de cara a la elaboración de un consentimiento informado y de la emisión de un informe de microarray prenatal, especialmente en el caso de la posible definición de variantes de significado incierto; las limitaciones inherentes a la técnica que deben ser tenidas en cuenta a la hora de recomendar su uso diagnóstico; así como un algoritmo pormenorizado de situaciones clínicas, donde se recomienda el uso de microarrays y su incorporación a la rutina clínica en el contexto de otras pruebas genéticas, incluyendo embarazos con antecedentes familiares o hallazgos sugerentes de un síndrome concreto, translucencia nucal incrementada en el primer trimestre o cardiopatía congénita en el segundo trimestre y hallazgos ecográficos no relacionados con un síndrome conocido o específico. Esta guía ha sido coordinada por la Asociación Española de Diagnóstico Prenatal (AEDP), la Asociación Española de Genética Humana (AEGH) y la Sociedad Española de Genética Clínica y Dismorfología (SEGCyD) (AU)

Microarray technology, recently implemented in international prenatal diagnosis systems, has become one of the main techniques in this field in terms of detection rate and objectivity of the results. This guideline attempts to provide background information on this technology, including technical and diagnostic aspects to be considered. Specifically, this guideline defines: the different prenatal sample types to be used, as well as their characteristics (chorionic villi samples, amniotic fluid, fetal cord blood or miscarriage tissue material); variant reporting policies (including variants of uncertain significance) to be considered in informed consents and prenatal microarray reports; microarray limitations inherent to the technique and which must be taken into account when recommending microarray testing for diagnosis; a detailed clinical algorithm recommending the use of microarray testing and its introduction into routine clinical practice within the context of other genetic tests, including pregnancies in families with a genetic history or specific syndrome suspicion, first trimester increased nuchal translucency or second trimester heart malformation and ultrasound findings not related to a known or specific syndrome. This guideline has been coordinated by the Spanish Association for Prenatal Diagnosis (AEDP, «Asociación Española de Diagnóstico Prenatal»), the Spanish Human Genetics Association (AEGH, «Asociación Española de Genética Humana») and the Spanish Society of Clinical Genetics and Dysmorphology (SEGCyD, «Sociedad Española de Genética Clínica y Dismorfología») (AU)

Recommendations for the use of microarrays in prenatal diagnosis. / Recomendaciones para el uso de microarrays en el diagnóstico prenatal.

Microarray technology, recently implemented in international prenatal diagnosis systems, has become one of the main techniques in this field in terms of detection rate and objectivity of the results. This guideline attempts to provide background information on this technology, including technical and diagnostic aspects to be considered. Specifically, this guideline defines: the different prenatal sample types to be used, as well as their characteristics (chorionic villi samples, amniotic fluid, fetal cord blood or miscarriage tissue material); variant reporting policies (including variants of uncertain significance) to be considered in informed consents and prenatal microarray reports; microarray limitations inherent to the technique and which must be taken into account when recommending microarray testing for diagnosis; a detailed clinical algorithm recommending the use of microarray testing and its introduction into routine clinical practice within the context of other genetic tests, including pregnancies in families with a genetic history or specific syndrome suspicion, first trimester increased nuchal translucency or second trimester heart malformation and ultrasound findings not related to a known or specific syndrome. This guideline has been coordinated by the Spanish Association for Prenatal Diagnosis (AEDP, «Asociación Española de Diagnóstico Prenatal¼), the Spanish Human Genetics Association (AEGH, «Asociación Española de Genética Humana¼) and the Spanish Society of Clinical Genetics and Dysmorphology (SEGCyD, «Sociedad Española de Genética Clínica y Dismorfología¼).

Clinical comparison of 10q26 overlapping deletions: delineating the critical region for urogenital anomalies.

The 10q26 deletion syndrome is a clinically heterogeneous disorder. The most common phenotypic characteristics include pre- and/or postnatal growth retardation, microcephaly, developmental delay/intellectual disability and a facial appearance consisting of a broad nasal bridge with a prominent nose, low-set malformed ears, strabismus, and a thin vermilion of the upper lip. In addition, limb and cardiac anomalies as well as urogenital anomalies are occasionally observed. In this report, we describe three unrelated females with 10q26 terminal deletions who shared clinical features of the syndrome, including urogenital defects. Cytogenetic studies showed an apparently de novo isolated deletion of the long arm of chromosome 10, with breakpoints in 10q26.1, and subsequent oligo array-CGH analysis confirmed the terminal location and defined the size of the overlapping deletions as ∼ 13.46, ∼ 9.31 and ∼ 9.17 Mb. We compared the phenotypic characteristics of the present patients with others reported to have isolated deletions and we suggest that small 10q26.2 terminal deletions may be associated with growth retardation, developmental delay/intellectual disability, craniofacial features and external genital anomalies whereas longer terminal deletions affecting the 10q26.12 and/or 10q26.13 regions may be responsible for renal/urinary tract anomalies. We propose that the haploinsufficiency of one or several genes located in the 10q26.12-q26.13 region may contribute to the renal or urinary tract pathogenesis and we highlight the importance of FGFR2 and probably of CTBP2 as candidate genes.

Array CGH detection of a novel cryptic deletion at 3q13 in a complex chromosome rearrangement.

Complex chromosome rearrangements (CCRs) are extremely rare in humans. About 20% of the apparently balanced CCRs have an abnormal phenotype and the degree of severity correlates with a higher number of breakpoints. Several studies using FISH and microarray technologies have shown that deletions in the breakpoints are common although duplications, insertions and inversions have also been detected. We report a patient with two simultaneous reciprocal translocations, t(3;4) and t(2;14;18), involving five chromosomes and six breakpoints. He showed dysmorphic features, preaxial polydactyly in the left hand, brachydactyly, postnatal growth retardation and developmental delay. The rearrangement was characterized by FISH analysis which detected an interstitial segment from chromosome 14 inserted in the derivative chromosome 2, and by whole genome array which revealed an interstitial deletion of approximately 4.5 Mb at the breakpoint site on chromosome 3. To our knowledge this microdeletion has not been previously reported and includes ~12 genes. The haploinsufficiency of one or several of these genes is likely to have contributed to the clinical phenotype of the patient.

Pre- and postnatal findings in a patient with a novel rec(8)dup(8q)inv(8)(p23.2q22.3) associated with San Luis Valley syndrome.

San Luis Valley syndrome, which is due to a recombinant chromosome 8 (SLV Rec8) found in Hispanic individuals from Southwestern United States, is a well-established syndrome associated with intellectual disabilities and, frequently, severe cardiac anomalies. We report for the first time on a Moroccan girl with a recombinant chromosome 8 prenatally diagnosed as SLV Rec8 by conventional cytogenetic studies. At birth, an oligo array-CGH (105 K) defined the breakpoints and the size of the imbalanced segments, with a deletion of ≈ 2.27 Mb (8p23.2-pter) and a duplication of ≈ 41.93 Mb (8q22.3-qter); thus this recombinant chromosome 8 differed from that previously reported in SLV Rec8 syndrome. The phenotypic characteristics associated with this SLV Rec8 genotype overlap those commonly found in patients with 8q duplication reported in the literature. We review SLV Rec8 and other chromosome 8 aberrations and suggest that the overexpression of cardiogenic genes located at 8q may be the cause of the cardiac defects in this patient.

Performance evaluation of biochemical and ultrasound markers for the screening of chromosomal numerical abnormalities in the first trimester of pregnancy.

BACKGROUND: To estimate the effectiveness of the first-trimester combined screening test in our population, departing from the results of diagnostic sensitivity and false positive rate (FPR), and checking some important parameters in prenatal screening. METHODS: The test was evaluated on 14250 pregnant women. The following variables were studied: the number of invasive techniques and the reasons for using such techniques, newborns with chromosomal abnormalities, total number of births, variation of biochemical markers throughout the gestational weeks, and MoM (multiple of the median) for biochemical and ultrasound markers. RESULTS: An important coverage and a decreased number of invasive techniques were obtained. For our population of pregnant women, the best gestational week to determine free beta-hCG and PAPP-A would be week 11 in which the best discrimination was found between affected and non affected fetuses for the three trisomies researched. We propose the cut-off 1/350, because it is the best one to increase sensitivity without exceeding the 5% FPR. CONCLUSIONS: Combined screening should be offered to pregnant woman, preferentially at week 11. Although different cut-offs for this prenatal test have been recommended by scientific societies, biochemical laboratories should set their own cut-off for getting the best sensitivity and FPR results. There should be a good level of collaboration between the laboratory and each participating ultrasound unit in order to ensure an optimal use of the first-trimester combined screening test.

Management of a dichorionic twin pregnancy with a normal fetus and an androgenetic diploid complete hydatidiform mole.

We describe a rare case of complete hydatidiform mole with twin live fetus (CHMTF) confirmed by histopathology, flow cytometry, and polymerase chain reaction techniques. No malformations were observed, fetal karyotype was normal and ß-human chorionic gonadotropin levels were increased (>100,000 IU/ml). Once the patient had been informed of the risks, it was decided to continue the pregnancy, but termination of pregnancy was necessary at week 13 + 5 due to maternal complications consisting of hyperthyroidism, hypertension and vaginal bleeding, followed by persistent trophoblastic disease (PTD). Patients diagnosed with CHMTF should be informed of all known risks, including the considerable risk of PTD, which is similar to - or according to some reports - even higher than that associated with a singleton complete mole and is not increased by continuing pregnancy. Due to the low number of series published, evidence-based clinical management guidelines are lacking.

Rapp-Hodgkin syndrome and SHFM1 patients: delineating the p63-Dlx5/Dlx6 pathway.

Rapp-Hodgkin Syndrome (RHS) is a genetic disorder resulting from mutations in the TP63 gene encoding p63 transcription factor. p63 is directly associated with a cis-regulatory element on chromosome 7q21 that controls the expression of DLX5 and DLX6 genes which are involved in craniofacial abnormalities and ectrodactyly or split hand/foot malformation (SHFM). Chromosomal deletions on 7q21 locus can result in loss of DXL5/DLX6 and/or in loss/disruption of cis-regulatory elements, at which p63 binds. We report two patients that have in common a p63-Dlx5/Dlx6 pathway dysregulation. One showed growth retardation, craniofacial dysmorphism, syndactyly, developmental delay and a de novo deletion (~8.5Mb) on chromosome 7q21.13-q21.3, including DLX5 and DLX6. The second patient with a clinical diagnosis of RHS showed a de novo heterozygous missense mutation, c. 401G>A (p.G134D), in TP63 (exon 4). Our findings may contribute to a greater understanding of the pathogenic mechanisms underlying disorders caused by TP63 mutations.

Evaluación de la eficacia del cribado prenatal del primer trimestre de embarazo en la Región de Murcia / Assessing the effectiveness of prenatal first trimester screening of pregnancy in the Region of Murcia

Introducción. El test combinado del primer trimestre permite seleccionar a las gestantes con un riesgo elevado de portar un feto con cromosomopatía con una sensibilidad y especificidad elevadas. Estas gestantes tras consejo genético pueden decidir someterse a una técnica invasiva para confirmar el diagnóstico. El objetivo de este trabajo es calcular la sensibilidad, el valor predictivo negativo y la tasa de falsos positivos del test combinado del primer trimestre en nuestro laboratorio. Material y métodos. Se estudiaron 4.494 gestantes (incluidas tanto las de embarazo único como gemelar) a las que se realizó el test combinado del primer trimestre: PAPP-A, b-HCG libre y translucencia nucal. Se comprobó el resultado del cariotipo en las gestantes cuyo cribado fue de riesgo elevado para Síndrome de Down (SD), de Edwards (SE) o ambos. En aquellas gestantes que decidieron no someterse a técnicas diagnósticas invasivas, se utilizó el cariotipo de los recién nacidos. El riesgo se calculó con el programa Prisca v.4.0.15.9® de DPC Dipesa® considerándose elevado un riesgo >1/270. Resultados. De todas las gestantes estudiadas, 260 mostraron un riesgo elevado: 201 para SD, 39 para SE y 20 para ambos. Se obtuvieron para SD y SE, respectivamente: verdaderos positivos (VP): 5 y 5; falsos positivos (FP): 216 y 54; verdaderos negativos (VN): 4273 y 4435; falsos negativos (FN): 0 y 0; Sensibilidad (S): 100% para ambos; Especificidad (E): 95% y 99%. Valor predictivo positivo (VPP): 2% y 8%; valor predictivo negativo(VPN): 100% para ambos. La tasa de falsos positivos fue del 4,83% para SD y de 1,20% para SE. Conclusiones. El cribado del primer trimestre es una herramienta eficaz que permite seleccionar a las gestantes con un riesgo >1/270 de portar un feto con cromosomopatía con una sensibilidad, especificidad y valor predictivo negativo elevados. Además su realización conlleva una disminución del número de técnicas diagnósticas invasivas (AU)

Introducción. El test combinado del primer trimestre permite seleccionar a las gestantes con un riesgo elevado de portar un feto con cromosomopatía con una sensibilidad y especificidad elevadas. Estas gestantes tras consejo genético pueden decidir someterse a una técnica invasiva para confirmar el diagnóstico. El objetivo de este trabajo es calcular la sensibilidad, el valor predictivo negativo y la tasa de falsos positivos del test combinado del primer trimestre en nuestro laboratorio. Material y métodos. Se estudiaron 4.494 gestantes (incluidas tanto las de embarazo único como gemelar) a las que se realizó el test combinado del primer trimestre: PAPP-A, b-HCG libre y translucencia nucal. Se comprobó el resultado del cariotipo en las gestantes cuyo cribado fue de riesgo elevado para Síndrome de Down (SD), de Edwards (SE) o ambos. En aquellas gestantes que decidieron no someterse a técnicas diagnósticas invasivas, se utilizó el cariotipo de los recién nacidos. El riesgo se calculó con el programa Prisca v.4.0.15.9(R) de DPC Dipesa(R) considerándose elevado un riesgo >1/270. Resultados. De todas las gestantes estudiadas, 260 mostraron un riesgo elevado: 201 para SD, 39 para SE y 20 para ambos. Se obtuvieron para SD y SE, respectivamente: verdaderos positivos (VP): 5 y 5; falsos positivos (FP): 216 y 54; verdaderos negativos (VN): 4273 y 4435; falsos negativos (FN): 0 y 0; Sensibilidad (S): 100% para ambos; Especificidad (E): 95% y 99%. Valor predictivo positivo (VPP): 2% y 8%; valor predictivo negativo (VPN): 100% para ambos. La tasa de falsos positivos fue del 4,83% para SD y de 1,20% para SE. Conclusiones. El cribado del primer trimestre es una herramienta eficaz que permite seleccionar a las gestantes con un riesgo >1/270 de portar un feto con cromosomopatía con una sensibilidad, especificidad y valor predictivo negativo elevados. Además su realización conlleva una disminución del número de técnicas diagnósticas invasivas (AU)

Molecular characterization of a new patient with a non-recurrent inv dup del 2q and review of the mechanisms for this rearrangement.

We report on newborn baby with microcephaly, facial anomalies, congenital heart defects, hypotonia, wrist contractures, long fingers, adducted thumbs, and club feet. Cytogenetic studies revealed an inverted duplication with terminal deletion (inv dup del) of 2q in the patient and a paternal 2qter deletion polymorphism. Microsatellite markers demonstrated that the inv dup del was maternal in origin and intrachromosomal. Intra or interchromosomal rearrangements may cause this aberration either by a U-type exchange (end-to-end fusion), an unequal crossover between inverted repeats (non-allelic homologous recombination: NAHR), or through breakage-fusion-bridge (BFB) cycles leading to a sister chromatid fusion by non-homologous end joining (NHEJ). A high-resolution oligo array-CGH (244 K) defined the breakpoints and did not detect a single copy region with a size exceeding 12.93 Kb in the fusion site. The size of the duplicated segment was 38.75 Mb, extending from 2q33.1 to 2q37.3 and the size of the terminal deletion was 2.85 Mb in 2q37.3. Our results indicate that the inv dup del (2q) is likely a non-recurrent chromosomal rearrangement generated by a NHEJ mechanism. The major clinical characteristics associated with this 2q rearrangement overlap with those commonly found in patients with 2q duplication reported in the literature.

Characterization of a de novo complex chromosomal rearrangement in a patient with cri-du-chat and trisomy 5p syndromes.

Two syndromes with abnormalities of the short arm of chromosome 5 have been described: cri-du-chat (resulting from 5p deletion) and trisomy 5p. We report for the first time a patient with both syndromes, resulting from a complex chromosomal rearrangement with an inverted duplication of 5p13.1-p14.2, a deletion of 5p14.2-pter, and a duplication of 5p12, characterized by array-CGH and BAC clones. The patient showed phenotypic characteristics of both syndromes and died at 3 months of age as a result of cardiorespiratory failure, probably associated with the clinical severity of the trisomy 5p syndrome. We propose a potential causative mechanism for this rearrangement.

Partial mole with a diploid fetus: case study and literature review.

OBJECTIVE: To describe an extremely rare case of a partial hydatidiform mole with a normal fetus. The etiology and clinical management of this entity are discussed. METHOD: Case report. RESULTS: We describe a rare case of partial mole and a living fetus of diploid karyotype and biparental origin confirmed by flow cytometry and PCR techniques. No malformations were observed, beta-hCG levels were high (>100,000 mIU/ml) and persistent trophoblastic disease did eventually occur. CONCLUSION: A suspected partial mole on ultrasound with increased beta-hCG and a sonographically normal living fetus of a diploid karyotype poses a dilemma for clinical management. Termination of pregnancy is not indicated if the fetus is normal; in fact, continuation to birth is possible in nearly 60% of cases with no increase in maternal risks when the patient is closely monitored after birth until beta-hCG is negative. In the case presented, however, a spontaneous abortion occurred at 21 weeks' gestation, possibly as a result of the amniocentesis.

Intrachromosomal partial triplication of chromosome 13 secondary to a paternal duplication with mild phenotypic effect.

Intrachromosomal triplications are rare and can be mistaken for duplications. The majority of triplications reported are de novo, mostly involving chromosome 15q, and have a middle inverted repeat. We report on the clinical, cytogenetic, and molecular analyses of a patient with a novel triplication 13q21.1-q21.33 secondary to a familial duplication 13q21.1-q21.33 with mild phenotypic effect in three generations. The propositus was an 8-year-old boy referred because of language delay and mild mental retardation. His weight, height and OFC were above the 97th centile. He had delayed tooth eruption and subtle dysmorphic features. Chromosome analysis (550 band stage) showed extra material in 13q21. Family history was unremarkable except for adult-onset sensorineural hearing loss in the father and paternal grandfather. Their karyotypes and those of both brothers of the propositus also showed an abnormal chromosome 13 but with less extra genetic material. FISH analysis with several BAC clones showed a triplication in the propositus between 204N9 and 184B18 (which mapped to 13q21.1 and 13q21.33, respectively) and a direct duplication for the same fragment (around 12 Mb) in the rest of the family members with the abnormal chromosome 13. The FISH signals did not show a middle inverted repeat. We describe the first intrachromosomal triplication 13q21.1-q21.33 derived from a paternal duplication. Meiotic instability in the transmission of a duplication has not been previously observed. Phenotypic variability may be explained by chromosomal non-penetrance or dosage critical loci located in the triplicate/duplicate segment.