A highly specific coding system for structural chromosomal alterations.

The Spanish Collaborative Study of Congenital Malformations (ECEMC, from the name in Spanish) has developed a very simple and highly specific coding system for structural chromosomal alterations. Such a coding system would be of value at present due to the dramatic increase in the diagnosis of submicroscopic chromosomal deletions and duplications through molecular techniques. In summary, our new coding system allows the characterization of: (a) the type of structural anomaly; (b) the chromosome affected; (c) if the alteration affects the short or/and the long arm, and (d) if it is a non-pure dicentric, a non-pure isochromosome, or if it affects several chromosomes. We show the distribution of 276 newborn patients with these types of chromosomal alterations using their corresponding codes according to our system. We consider that our approach may be useful not only for other registries, but also for laboratories performing these studies to store their results on case series. Therefore, the aim of this article is to describe this coding system and to offer the opportunity for this coding to be applied by others. Moreover, as this is a SYSTEM, rather than a fixed code, it can be implemented with the necessary modifications to include the specific objectives of each program.

Pautas de prevención de defectos congénitos con especial referencia a los niveles primario y secundario. Guías de actuación preventiva desde la atención primaria / Guidelines for the prevention of congenital defects, particularly at primary and secondary level. Prevention guidelines from Primary Care

La prevención de defectos congénitos (DC) no difiere en esencia de la que se sigue para cualquier otra enfermedad. En el primer nivel, el de la prevención primaria, se trata de impedir que se produzca el trastorno. El segundo nivel se aplica cuando el DC ya se ha producido, y consiste en curar la enfermedad o, cuando ello no es posible, como en la mayoría de los DC, evitar que se agrave. Este nivel se basa en el diagnóstico precoz y correcto de la enfermedad, y en instaurar inmediatamente el tratamiento adecuado y las medidas correctoras o paliativas. El tercer nivel se instaura una vez que han fracasado los 2 anteriores y se centra en medidas que mejoren la autonomía y la calidad de vida del paciente (integración social y laboral de los afectados, supresión de barreras arquitectónicas, etc.). Por último, existe un «cuarto nivel de prevención» que consiste en evitar toda sobreactuación médica, en la que se someta al paciente a pruebas innecesarias que no sólo no le ayudan sino que, además, pueden generarle efectos adversos añadidos incluyendo problemas psíquicos. En este artículo se resumen las medidas más relevantes que se deberían implantar desde el colectivo de médicos de atención primaria, para conseguir todos los niveles de prevención de DC y, especialmente, de prevención primaria (AU)

There is essentially no difference in the prevention of congenital defects (CD) from that of any other disease. Primary prevention consists of preventing the causes that produce the disease. Secondary prevention is applied when the CD has already occurred, and consists of curing the disease, or when this is not possible, as in the majority of CD, to prevent it getting worse. This level is based on the early and correct diagnosis of the disease, and initiating immediate and appropriate treatment and corrective or palliative measures. The third level is started when the previous ones fail, and is focussed on measures that improve independence and quality of life (social and occupational integration of those affected, removal of architectural obstacles, etc.). Lastly, there is a “fourth level of prevention”, which consists of avoiding over-medication, in which the patient is subjected to unnecessary tests, which not only do not help the patient, but can also produce added adverse effects, including psychiatric problems. This article summarises the most important measures that Primary Care doctors should introduce to achieve all levels of CD prevention, and particularly primary prevention (AU)

Thanatophoric dysplasia type II with encephalocele and semilobar holoprosencephaly: Insights into its pathogenesis.

Thanatophoric dysplasia (TD) is a lethal form of short-limb skeletal dysplasia that is associated with macrocephaly, and variably cloverleaf skull. Two types of TD are clinically recognized, TD1 and TD2, mainly distinguished by their radiographic characteristics. The differences between the two are principally observed in the femur, which appears curved in TD1, while it remains straight but with a proximal medial spike in TD2, and are a less severe overall affectation in TD2. Both types of TD are caused by mutations in different functional domains of the FGFR3 gene. However, whereas several mutations in the different domains of FGFR3 cause TD1, the K650E mutation involving the change of a lysine to glutamic acid ("Lys650Glu") has been found in all TD2 cases to date. Here we describe a newborn infant with TD2 associated with brain defects that have either been infrequently observed (encephalocele) or not hitherto described (holoprosencephaly). Based on recent studies, we consider encephaloceles described in TD to be pseudoencephaloceles, since they are secondary to the intracranial pressure generated by severe hydrocephaly and to severe cranial structural anomalies. Finally, to analyze the mechanisms of holoprosencephaly observed in the case described here, we include a concise review on the current understanding of how FGFs and their receptors are expressed in the rostral signaling center (particularly Fgf8). In addition, we evaluated recent observations that FGF ligands and receptors (including FGFR3) act in concert to organize the whole telencephalon activity, rather than independently patterning different areas.

Ejemplos clínicos de alteraciones crípticas del ADN, y guías para sospechar que un niño pueda tener alguna alteración críptica o molecular / Examples of DNA cryptic alterations, and guidelines for suspecting a child may have cryptic genetic or molecular alterations

No siempre es posible establecer el diagnóstico de un recién nacido con defectos congénitos. En general esto se debe a varias causas fundamentales: a) porque el conjunto de manifestaciones clínicas que presentan son aún de causa desconocida; b) porque los síndromes que ya se conocen tienen una frecuencia tan baja que no son fáciles de reconocer cuando no se tiene experiencia previa; c) porque no existe especificidad alguna entre una causa y un defecto; d) porque algunos solo presentan rasgos dismórficos que solo con gran experiencia pueden ser evaluados, ya que la mayoría de esos rasgos se encuentran en la población general sana, y e) porque muchos de ellos son de aparición evolutiva siendo de apariencia normal al nacimiento. Sin embargo, hoy se sabe que algunos de estos síndromes son producidos por alteraciones debidas a pérdidas de porciones cromosómicas tan pequeñas que no se detectan por citogenética de alta resolución (son crípticas para estas técnicas) o a mutaciones conocidas de ciertos genes. Como muchos de estos niños van a ir presentando sus manifestaciones durante la infancia, van a ser atendidos por los médicos de atención primaria, por lo que es esencial que dispongan de unas pequeñas guías para su reconocimiento y su manejo adecuado. En este artículo se explican las diferentes formas de presentación, sus características, las técnicas con las que se pueden diagnosticar, así como los síntomas que pueden alertar sobre estos síndromes y forma de actuar. Porque de la identificación precoz depende mucho el pronóstico y la información a la familia (AU)

It is not always possible to establish the diagnosis of a newborn with congenital defects. In general, this is due to several main reasons: a) because the group of clinical signs that they show are still of an unknown cause; b) because the already known syndromes are such a low frequency that they are not easy to recognise when there is no previous experience; c) because there is no specificity between a cause and a defect; d) because some only present with dysmorphic characteristics that can only be assessed by someone with wide experience since the majority of these characteristics are found in the general healthy population; and e) because many of them appear over time, appearing normal at birth. However, it is now known that some of these syndromes are caused by changes due to the loss of chromosome portions so small that they are not detected by high resolution cytogenetics (they are cryptic for these techniques), or to known mutations in certain genes. As many of these children will present with their signs during childhood and are going to be seen by Primary Care doctors, it is essential that small guises are available to recognise them and manage them appropriately. This article explains the different forms of presentation, their technical characteristics by which they can be diagnosed, as well as the symptoms that may make us aware of these syndromes and how to act. The prognosis very much depends on early identification and information to the family (AU)

Tratamiento farmacológico de la mujer embarazada: fármacos contraindicados durante la gestación / Pharmacological treatment in the pregnant woman: drugs contraindicated during pregnancy

Los médicos de atención primaria atienden a las mujeres embarazadas y en edad reproductiva, por lo que han de decidir sobre el tratamiento que deben seguir. Para ello, han de enfrentarse a la difícil situación de evaluar el riesgo que las diferentes alternativas terapéuticas pueden suponer para el desarrollo embrionario/fetal. Una evaluación que no es sencilla porque no se pueden establecer normas de aplicación general. De hecho, un mismo medicamento puede ser utilizado en algunas mujeres embarazadas y no ser adecuado en otras. Esto implica que la decisión sobre el tratamiento que se debe aplicar durante el embarazo requiera una evaluación individualizada en cada mujer. Por otra parte, la identificación del efecto de los diferentes medicamentos sobre el desarrollo embrionario y fetal humano es muy difícil y, además, está generalmente basada en estudios epidemiológicos observacionales. Esto supone una dificultad añadida porque en muchos casos este tipo de publicaciones no resultan fáciles de entender, lo que dificulta su traslación a la práctica clínica. Esto dio lugar en muchos países a la organización de servicios de información telefónica sobre teratógenos, atendidos por expertos tanto en evaluación de los riesgos para el embrión y feto, como sobre los procesos del desarrollo prenatal. No obstante, sabemos que hay fármacos que no parecen alterar el desarrollo y que pueden utilizarse durante el embarazo si se necesitan, otros que sí conllevan riesgo pero tienen que utilizarse para controlar la enfermedad materna y, por último se conocen otros cuya utilización en mujeres embarazadas o que planean estarlo está contraindicada. Estos últimos en mujeres en edad reproductiva han de utilizarse siguiendo unas estrictas normas para prevención de embarazos. En este artículo se ofrece una visión general sobre los tratamientos en mujeres embarazadas o que pueden estarlo, junto con sus potenciales efectos y se ofrece la lista de aquellos fármacos que se consideran seguros de utilizar durante la gestación y los que están contraindicados (AU)

As primary care doctors treat pregnant women and those of fertile age, they must decide which treatments they should follow. Therefore, they have to confront the difficult situation of assessing the risks that different alternative treatments may have on embryo/foetal development. An assessment that is not straightforward as established general guidelines may not be applicable. For example, one drug may be used in some pregnant women but may not be appropriate in others. This implies that the decision on treatments given during pregnancy requires an individualised assessment in each woman. On the other hand, identifying the effects of different drugs on human embryo and foetal development is very difficult, and is also mainly based on observational epidemiological studies. This makes it even more difficult as in many cases these publications are not easy to understand, making it difficult to apply in clinical practice. This has led to introducing Telephone Information Services on Teratogenics in many countries, which are answered by experts in the assessment of risks for the embryo and foetus, as well as on the processes of prenatal development. However, we know that there are drugs that do not seem to affect this development and can be used during pregnancy if required. Similarly, others are also known to be used in pregnant women or those planning a pregnancy are totally contraindicated. For this reason, women who take these have to follow strict guidelines to prevent becoming pregnant. This article provides a general view on treatments for pregnant women or those planning a pregnancy, together with their potential effects, as well as a list of those drugs that may be considered safe to use during pregnancy, and those that are contraindicated (AU)

Resumen de la evolución de las técnicas de citogenética y genética molecular para la identificación de las alteraciones genéticas del desarrollo embrionario / Review of the development of molecular cytogenetic and genetic techniques for identifying genetic anomalies in embryonic development

Desde la última mitad del siglo xx se ha producido un espectacular progreso en el conocimiento sobre el material genético humano: se han caracterizado los cromosomas, se ha identificado la secuencia completa del genoma y se ha relacionado un gran número de alteraciones de la estructura y secuencia del ADN con todo tipo de enfermedades, tanto hereditarias como no hereditarias (especialmente asociadas a cáncer). Este desarrollo ha venido propiciado, y acompañado, por una gran cantidad de técnicas para su estudio, muchas de las cuales se han trasladado a la investigación y la caracterización de la carga genética de los seres humanos, y a su aplicación en la práctica clínica para el diagnóstico de ciertas patologías. Ello ha generado que, además de los estudios moleculares al nivel de identificación de la mutación de un gen, la citogenética convencional se haya ampliado a la detección de alteraciones extremadamente pequeñas de la estructura del cromosoma, dando lugar a una nueva área de diagnóstico denominada citogenética molecular. Esta incluye diversas técnicas que detectan alteraciones pequeñas en orden decreciente, desde las micro-deleciones y micro-duplicaciones detectables por sondas fluorescentes (FISH), hasta los arrays genómicos y los arrays basados en hibridación genómica comparada (CGH) que detectan cambios aun más pequeños. Sin embargo, debido a su alta resolución, los arrays son capaces de identificar variaciones en el ADN cuyo significado, en muchos casos, es aun incierto. Esto implica que incluso algunas de las técnicas que más se están utilizando en la actualidad, como la CGH array, precisen de una cuidadosa evaluación antes de ofrecer un diagnóstico (AU)

Spectacular progress has been made in the knowledge of human genetic material since the middle of the last century: the chromosomes have been characterised; the complete sequence of the genome has been identified. Also, all types of diseases hereditary and non-hereditary diseases (especially cancers) have been associated to changes in DNA structure and sequence. These developments have been accompanied by a great number of techniques, which have led to the investigation and characterisation of the human genetic load, and its application in clinical practice for the diagnosis of certain diseases. This has meant that, besides studies at molecular level for identifying a gene mutation, conventional cytology has extended to the detection of extremely small changes in the structure of the chromosome, giving rise to a new area of diagnosis called molecular cytogenetics. This includes various techniques that detect small changes, in decreasing order, from microdeletions and microduplications detectable by fluorescent probes (FISH), to genomic arrays and arrays based on compared genomic (CGH) which detect even smaller changes. However, due to their high resolution, arrays are capable of identifying variations in DNA, which in many cases its importance is still uncertain. This implies that even some of the most common techniques currently used, such as CGH, require a careful evaluation before offering a diagnosis (AU)

Estructura y función del ADN y de los genes II. Tipos de alteraciones de la función del gen por procesos epigenéticos / Structure and function of DNA and of the genes II. Types of alterations of the gene function through epigenetic processes

El tipo de cambios en la función del gen que vamos a resumir en este artículo, no se deben a alteraciones en la estructura del ADN, en ninguno de sus niveles de resolución (mutaciones, pérdidas y ganancias de material, tanto invisibles como visibles por citogenética). Son cambios producidos por procesos epigenéticos, que sin alterar la estructura de la molécula de ADN, si alteran su función (AU)

The type of changes in the gene function we are going to summarize in this article are not due to alterations in DNA structure, in any of their resolution levels (mutations, material loss and gains, both invisible and visible by cytogenetic). They are changes produced by epigenetic processes, which although they do not alter the DNA molecular structure, they do alter its function (AU)

Subtelomeric deletion of 12p: Description of a third case and review.

Only 12 cases with a cytogenetically visible deletion of the short arm of chromosome 12 (12p) have been reported so far. The difference in clinical features observed in these patients indicates that there is no distinct phenotype associated with this short arm deletion, although the existence of a del(12p) syndrome was previously suggested. Besides those 12 reports, only two patients have been described with a subtelomeric 12p deletion; both present in the same family in which the son showed a mild phenotype of moderate mental retardation and behavioral problems and his carrier mother had no apparent phenotype. In this article, we describe the third known patient with a subtelomeric 12p deletion in a young boy with mental retardation and microcephaly, and review the literature.

Estructura y función del ADN y de los genes. I Tipos de alteraciones de la función del gen por mutaciones / Structure and function of the DNA and genes. Types of alterations of the gene function through mutations

El ADN es «la molécula de la vida», y es la que lleva codificada la información genética característica de los diferentes seres vivos. Mediante ese código, regula el funcionamiento de cada tipo de célula; controla la transmisión de esa información, tanto en el tiempo como en el lugar de actuación de la misma; coordina la complejísima red de interacciones del funcionamiento celular y tisular; controla también su propia duplicación, reparación y autorregulación. Igualmente, controla y coordina los procesos de reproducción y mantenimiento de las características de cada especie. Todas estas actividades funcionales son reguladas y conducidas por un conjunto de instrucciones que constituyen el llamado código genético. El resultado se basa en un equilibrio entre la influencia del ambiente y esta compleja red funcional del ADN que muestra, además, un muy alto grado de plasticidad. Por ello, el genoma puede producir respuestas adecuadas a diferentes cambios del ambiente, manteniendo ese equilibrio. No obstante, a pesar de la importante capacidad homeostática del genoma, es susceptible de sufrir alteraciones por ciertos agentes que modifican el ambiente, dando lugar a efectos adversos y patológicos (AU)

The DNA is the “molecule of life,” and is that which carries the coded genetic information of the different human beings. Through this code, the functioning of each type of cell is regulated. It controls the transmission of this information, both in its time and place of action. It coordinates the very complex network of interactions of the cell and tissue function. It also controls its own replication, repair and self-regulation. Furthermore, it controls and coordinates the reproduction and maintenance processes of the characteristics of each species. All these functional activities are regulated and conducted through a combination of instructions that make up the so-called genetic code. The result is based on a balance between environmental influence and this complex functional network of the DNA that also shows a very high plasticity grade. Thus, the genome can produce adequate responses to different environmental changes, maintaining this balance. However, in spite of the important hemostatic capacity of the genome, it can be altered by some agents that modify the environment, giving rise to adverse effects and pathologic conditions (AU)

Estructura y función del ADN y de los genes. I Tipos de alteraciones de la función del gen por mutaciones / Structure and function of the DNA and genes. Types of alterations of the gene function through mutations

El ADN es «la molécula de la vida», y es la que lleva codificada la información genética característica de los diferentes seres vivos. Mediante ese código, regula el funcionamiento de cada tipo de célula; controla la transmisión de esa información, tanto en el tiempo como en el lugar de actuación de la misma; coordina la complejísima red de interacciones del funcionamiento celular y tisular; controla también su propia duplicación, reparación y autorregulación. Igualmente, controla y coordina los procesos de reproducción y mantenimiento de las características de cada especie. Todas estas actividades funcionales son reguladas y conducidas por un conjunto de instrucciones que constituyen el llamado código genético. El resultado se basa en un equilibrio entre la influencia del ambiente y esta compleja red funcional del ADN que muestra, además, un muy alto grado de plasticidad. Por ello, el genoma puede producir respuestas adecuadas a diferentes cambios del ambiente, manteniendo ese equilibrio. No obstante, a pesar de la importante capacidad homeostática del genoma, es susceptible de sufrir alteraciones por ciertos agentes que modifican el ambiente, dando lugar a efectos adversos y patológicos (AU)

The DNA is the “molecule of life,” and is that which carries the coded genetic information of the different human beings. Through this code, the functioning of each type of cell is regulated. It controls the transmission of this information, both in its time and place of action. It coordinates the very complex network of interactions of the cell and tissue function. It also controls its own replication, repair and self-regulation. Furthermore, it controls and coordinates the reproduction and maintenance processes of the characteristics of each species. All these functional activities are regulated and conducted through a combination of instructions that make up the so-called genetic code. The result is based on a balance between environmental influence and this complex functional network of the DNA that also shows a very high plasticity grade. Thus, the genome can produce adequate responses to different environmental changes, maintaining this balance. However, in spite of the important hemostatic capacity of the genome, it can be altered by some agents that modify the environment, giving rise to adverse effects and pathologic conditions (AU)

Características generales de los defectos congénitos, terminología y causas / General characteristics of congenital defects, terminology and causes

El término general que se utiliza para denominar cualquier tipo de alteración del desarrollo embrionario y fetal humano, independientemente del momento del desarrollo en el que se produzca, es el de defectos (o anomalías) congénitos(as). Sin embargo, no todas las alteraciones del desarrollo embrionario y fetal se forman en el mismo momento, por ello, y dependiendo del periodo del desarrollo en el que se produzcan, van a recibir diferentes nombres. Así, lo que se entiende por malformaciones congénitas son las alteraciones físicas, que ocurren durante las primeras 10 semanas contando desde el primer día de la última regla (periodo embrionario). No obstante, hay algunas alteraciones físicas que se producen durante cualquier momento de las 30 semanas siguientes de embarazo (de la 11 a la 40) —que corresponde al periodo fetal— que no son verdaderas malformaciones. Para poder distinguir las que son malformaciones de las que no lo son, se ha establecido una terminola diferente. Así, para las que se forman después de la 10.a semana, que no son malformaciones, su denominación se basa generalmente en los mecanismos patogénicos.En este artículo se exponen y definen todos estos aspectos, así como las formas de presentación de los defectos congénitos en el niño recién nacido y los grandes grupos de causas(AU)

The general term used to call any type of embryonic and human fetal development, independently of the time of development in which it is produced, is that of congenital defects (or abnormalities). However, not all the embryonic and fetal development alterations are formed at the same time. Thus, depending on the development period in which they are produced, they receive different names. Therefore, what is understood as “congenital malformations” are physical alterations, that occur during the first 10 weeks beginning on the first day of the last menstruation (embryonic period). However, there are some physical alterations that may occur at any time during the next 30 weeks of the pregnancy (from 11 to 40) –that correspond to the fetal period – that are not truly malformations. In order to distinguish those that are malformation from those that are not, different terminology has been established. Thus, for those that occur after the 10th week, which are not malformations, their name is generally based on the pathogenic mechanisms.In this article, these aspects, as well as the presentation forms of the congenital defects in the newborn child and the large group of causes are explained and defined(AU)

Deleción 9p-. Disgenesia gonadal asociada a retraso mental e hipoplasia del cuerpo calloso. ¿Síndrome de genes contiguos? / Chromosome 9P deletion: Gonadal dysgenesis associated with mental retardation and hypoplasia of the corpus callosum: a contiguous gene syndrome

Antecedentes: Son muchos los genes que se han implicado en la diferenciación testicular, cuyas alteraciones dan cuadros de trastornos de la diferenciación sexual y cariotipo 46XY. Caso clínico: Recién nacido con hipospadias interescrotal, gónadas palpables y pene hipoplásico. Cariotipo 46XY. Ecografía abdominal: testes y sin restos müllerianos. Buena respuesta al test corto de gonadotropinas. Al año presenta retraso psicomotor, hipotonía. Resonancia magnética con atrofia de sustancia blanca frontotemporal y disminución del cuerpo calloso. Biopsia testicular compatible con disgenesia gonadal. Dada la situación intersexual al nacimiento, el retraso psicomotor y la presencia de dismorfias faciales se solicita cariotipo de alta resolución: deleción 46, XY, del(9p)(p23-pter).ish tel (9p-). Comentarios: Son muchos los genes implicados en la diferenciación testicular, algunos de ellos también influyen sobre el desarrollo de otros tejidos. En el brazo corto del cromosoma 9 se encuentran dos genes, DMRT1 y DMRT2, implicados en la diferenciación sexual, cuyas alteraciones también han sido descritas como causantes de retraso mental. En la evaluación de los trastornos de la diferenciación sexual son muy importantes los signos acompañantes para poder orientar el estudio genético (AU)

Background: Many genes are involved in testicular differentiation. The alterations of these genes are responsible for sexual differentiation disorders with 46 XY karyotype. Case: We report the case of a newborn who had an interscrotal hypospadias, palpable gonads and hypoplastic penis. Karyotype 46 XY. Abdominal ultrasound revealed testes and absence of Müllerian remnants. There was a good response to the short gonadotrophin test. At one year he had signs of psychomotor retardation and hypotonia. The magnetic resonance revealed frontal-temporal atrophy and a decrease in the corpus callosum. Testicular biopsy was compatible with gonadal dysgenesis. A preoperative cystography showed a vaginal remnant. Due to the presence of a sexual differentiation disorder, psychomotor retardation and facial dysmorphism, we requested a high-resolution karyotype: deletion 46, XY, del (9p) (p23-pter). Ish tel (9p-). Discussion: Many genes are involved in testicular differentiation, some of which also affect the development of other tissues. In the short arm of chromosome 9, two genes, DMRT1 and DMRT2, are involved in sexual differentiation. Their alterations have also been described as causing mental retardation. In the evaluation of 46,XY disorders of sex differentiation, the accompanying signs are very important for guiding the genetic study (AU)

[Chromosome 9P deletion: Gonadal dysgenesis associated with mental retardation and hypoplasia of the corpus callosum: A contiguous gene syndrome?]. / Deleción 9p-. Disgenesia gonadal asociada a retraso mental e hipoplasia del cuerpo calloso. ¿Síndrome de genes contiguos?

BACKGROUND: Many genes are involved in testicular differentiation. The alterations of these genes are responsible for sexual differentiation disorders with 46 XY karyotype. CASE: We report the case of a newborn who had an interscrotal hypospadias, palpable gonads and hypoplastic penis. Karyotype 46 XY. Abdominal ultrasound revealed testes and absence of Müllerian remnants. There was a good response to the short gonadotrophin test. At one year he had signs of psychomotor retardation and hypotonia. The magnetic resonance revealed frontal-temporal atrophy and a decrease in the corpus callosum. Testicular biopsy was compatible with gonadal dysgenesis. A preoperative cystography showed a vaginal remnant. Due to the presence of a sexual differentiation disorder, psychomotor retardation and facial dysmorphism, we requested a high-resolution karyotype: deletion 46, XY, del (9p) (p23-pter). Ish tel (9p-). DISCUSSION: Many genes are involved in testicular differentiation, some of which also affect the development of other tissues. In the short arm of chromosome 9, two genes, DMRT1 and DMRT2, are involved in sexual differentiation. Their alterations have also been described as causing mental retardation. In the evaluation of 46,XY disorders of sex differentiation, the accompanying signs are very important for guiding the genetic study.

A small and active ring X chromosome in a female with features of Kabuki syndrome.

A ring X chromosome is found in about 6% of patients with Turner syndrome (TS), often with mosaicism for a 45,X cell line. Patients with this karyotype are reported to have a higher incidence of a more severe phenotype including mental retardation. In fact, some studies have shown a correlation between this severity and the presence or absence of an intact and functional X inactivation center (XIST). However, the phenotype of the individuals with r(X) cannot be entirely defined in terms of their X-inactivation patterns. Nevertheless, a small group of these patients have been described to manifest clinical features reminiscent of the Kabuki syndrome. Here we present a female patient with clinical features resembling Kabuki syndrome and a mos 45,X/46,X,r(X) karyotype. Methylation analyses of polymorphic alleles of the androgen receptor gene showed that both alleles were unmethylated suggesting an active ring chromosome. A specific X chromosome array CGH was performed estimating the size of the ring to be 17 Mb, lacking the XIST gene, and including some genes with possible implications in the phenotype of the patient.

The biochemical structure and function of methylenetetrahydrofolate reductase provide the rationale to interpret the epidemiological results on the risk for infants with Down syndrome.

Studies on the structure of the methylenetetrahydrofolate reductase (MTHFR) gene and the mechanisms by which folate may reduce homocysteine levels in bacteria and in humans have provided a rationale to understand the conflicting epidemiological observations between the studies on the 677C-T and 1298A-C MTHFR polymorphic variants, and the risk of having an infant with Down syndrome (DS). However, three of the combined genotypes (CTCC, TTAC, and TTCC) are very infrequent in the human population. In fact, these three rare genotypes were only observed in two of the eight epidemiological studies that analyzed these genotype combinations and the risk of DS. In a study of the Indian population these three genotypes were identified in mothers of DS children but not in control mothers demonstrating a statistically significant increase in the risk of giving birth to DS infants. Conversely, the CTCC and TTAC genotypes were only observed in control mothers and not in mothers of DS infants in the Spanish study, while the TTCC genotype was not observed in any Spanish mother analyzed. These results were not related to the frequency of the T allele, since this was lower in the Indian population (21.4% among case mothers and 12.4% in control mothers) than in the Spanish population (33.9%). At present, several important biological aspects on the Hcy cycle are known, including: (a) the biochemical structure and function of the MTHFR enzyme, (b) the biological basis for the effect of the different 677C-T and 1298A-C MTHFR genotype combinations on Hcy levels, (c) that folate is not synthesized by the organism that obtained it from the diet, (d) that TT homozygotes will be at particular risk when their folate status is low because the mutant enzyme requires much higher levels of folate than the physiological one to stabilize the binding of flavin-adenosine-dinucleotide (FAD), (e) that the release of flavin is prevented by increasing the levels of folate, and (f) that the cystathionine-beta-synthase gene is located on chromosome 21. Together, these facts suggest that destabilization of the Hcy cycle in function of the levels of S-adenosylmethionine (SAM), may be modified by some embryonic and maternal genotypes, as well as by maternal nutritional status and life style. This may also influence the probability that some embryos survive to birth, but in different way for those with and without trisomy 21, as is discussed in this article.

Two new patients bearing mutations in the fukutin gene confirm the relevance of this gene in Walker-Warburg syndrome.

Walker-Warburg syndrome (WWS) is an autosomal recessive disorder characterized by congenital muscular dystrophy, brain malformations and structural abnormalities of the eye. We have studied two WWS patients born to non-consanguineous parents, and in both cases, we identified mutations in the fukutin gene responsible for this syndrome. One of the patients carries a homozygous-single nucleotide insertion that produces a frameshift, being this the first time that this insertion has been described in homozygosis and causing a WWS phenotype. The other patient carries two novel mutations, one being a point mutation that produces an amino acid substitution, while the other is a deletion in the 3'UTR that affects the polyadenylation signal of the fukutin gene. This deletion would probably result in the complete loss of the fukutin transcripts from this allele. This is the first time a mutation localized outside of the fukutin coding region has been identified as a cause of WWS.

Small supernumerary chromosome marker generating complete and pure trisomy 18p, characterized by molecular cytogenetic techniques and review.

Small supernumerary marker chromosomes (sSMC) have been described from all human chromosomes with different sizes and shapes. However, it is difficult to know the clinical manifestations associated with them, because such knowledge depends on the size, presence of euchromatic material, degree of mosaicism and/or uniparental disomy (UPD). Pure trisomy of the whole arm of chromosome 18 (18p), has been described in only a few cases and the general consensus is that there is a mild phenotypic effect. Here we report on a newborn male presenting with an atrial septal defect and a club foot. The high resolution G-band karyotype (550-850 bands) and the molecular cytogenetic techniques revealed in all cells the presence of an sSMC, which was a complex derivative from the short arm of a chromosome 18 (18p) and a centromere of a chromosome 13/21. His healthy mother had the same sSMC in all analyzed cells. With the present case, we support the previous suggestion that this unusual chromosome trisomy 18p has little clinical repercussions.

The first 4p euchromatic variant in a healthy carrier having an unusual reproductive history.

We report on the molecular cytogenetics studies in a healthy couple who had had three pregnancies which ended in a termination of pregnancy (TOP). In two of them, prenatal sonogram showed fetal dwarfism and in the third one, a chromosome alteration was found in the amniocentesis. A previous pregnancy ended in a healthy girl. A high-resolution G-band karyotype (550-850 bands), together with Fluorescence in situ Hybridization (FISH) techniques, detected in the father a 4p interstitial euchromatic duplication. This chromosome duplication appears to be a previously undescribed euchromatic variant (EV). We discuss the possibility that the 4p paternal EV could be involved in the clinical and genetic findings of the three TOPs.