Mosaicismo de trisomía 9: caso de larga supervivencia / Mosaic trisomy 9: report of a new case with a long-term survival

Introducción: La trisomía 9 es una aneuploidía infrecuente y, por tanto, difícil de sospechar. Objetivo: Comunicar un nuevo caso de mosaicismo de trisomía 9, de larga supervivencia, para contribuir al mejor conocimiento de sus características clínicas y pronóstico. Caso clínico: Primera hija de padres sanos. Retraso de crecimiento intrauterino asimétrico y oligohidramnios. Nace a las 34 semanas con 1.478 g de peso, depresión respiratoria y fenotipo anómalo: dolicocefalia; hipotelorismo, microftalmia, hendiduras palpebrales pequeñas; nariz de base ancha y punta en bulbo; micrognatia; orejas de implantación baja, y anomalías en las manos y los pies. Ausencia de malformaciones en los órganos internos. Cariotipo: normal (46,XX). A los 17 meses, ante el retraso psicomotor evidente y las alteraciones descritas se realiza un segundo cariotipo convencional insistiendo en el análisis de un mayor número de células. Se halla un mosaicismo de trisomía 9 (46,XX/47,XX, 1 9). Como dato fenotípico curioso, a los 24 meses aparece un incisivo único superior medial, no descrito antes en otros casos de trisomía 9. Actualmente, tiene 4 años, un retraso mental profundo y ninguna otra complicación. Comentarios: Destaca la mayor dificultad diagnóstica de los mosaicismos; por lo que se debe insistir en el análisis de un número suficiente de células al estudiar el cariotipo. Además, es importante su diagnóstico en sujetos con anomalías fenotípicas, para dar información correcta a los padres en orden a su pronóstico y a la futura descendencia (AU)

Introduction: Trisomy 9 is an uncommon chromosome abnormality that may be seen in a mosaic or non-mosaic state. Objective: To better define the phenotype and prognosis of this disorder we report a new case of mosaic trisomy 9 with a long-term survival. Clinical report: We present the case of a female patient, born from the first pregnancy of a healthy couple. Fetal ultrasounds disclosed intrauterine growth retardation and oligohydramnios. Cesarean section was performed in the 34th week. Birth weight was 1,478 g. Neonatal examination showed: dolichocephaly; hypotelorism, microphthalmia, short palpebral fissures; broad-based nose with bulbous tip; micrognathia; low-set malformed ears; abnormal hands and feet; no other malformations. The initial karyotype determination was normal (46,XX). At 17 months of age, a second karyotype was requested because the patient developed severe psychomotor retardation. Chromosome analysis showed mosaic trisomy 9 (46,XX/47,XX, 1 9). Six months later, a single upper central incisor was noted. To our knowledge, this feature has not been reported previously in the trisomy 9. The patient is now 4 years old. She shows severe psychomotor retardation, but no other complications. Comments: It is important to be aware of the possibility that mosaicism may exist in a patient with normal blood karyotype and abnormal phenotype. We conclude that a great number of cells is needed in order to obtain a correct karyotype diagnosis. Correct diagnosis is essential to define the prognosis and provide accurate genetic counseling (AU)

Hipertricosis localizada y mosaicismo pigmentario tipo Ito (hipomelanosis de Ito) / Localized hypertrichosis and pigmentary mosaicism of Ito (hypomelanosis of Ito)

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Lesiones cutáneas hipopigmentadas y facies particular / Hypopigmented skin lesions and coarse facies

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Nevo poroqueratósico de los ostios y ductos ecrinos / Porokeratotic eccrine ostial and dermal duct nevus

Se considera que el nevo poroqueratósico de los ostios y ductos ecrinos (NPODE) es un hamartoma del conducto sudoríparo. Presentamos el caso de una niña de un mes de edad que presentaba desde el nacimiento una erupción distribuida según las líneas de Blaschko en las extremidades y el tronco, con clara afectación palmoplantar. No se acompañaba de ningún otro defecto congénito y la paciente presentaba un desarrollo normal. La biopsia de una de las lesiones mostró los hallazgos típicos del nevo poroqueratósico de los ostios y ductos ecrinos. La anatomía patológica y las técnicas de inmunohistoquímica en este trastorno parecen revelar que la invaginación epidérmica en donde se halla la lámina paraqueratósica (similar a una lamela cornoide) es atravesada por un acrosiringio aparentemente normal. Dada la distribución de las lesiones y su aparición esporádica, el trastorno parece representar un mosaicismo genético (AU)

How clinicians add to knowledge of development.

Studies of human birth defects and developmental disorders have made major contributions to our understanding of development. Rare human syndromes have allowed identification of important developmental genes, and revealed mechanisms such as uniparental disomy and unstable trinucleotide repeats that were not suspected from animal studies. Some aspects of development, in particular cognitive development, can only be studied in human beings. Basic developmental mechanisms are very highly conserved across a very wide range of animals, making for a rich interplay between animal and human studies. Often, clinical studies identify a gene, or suggest a hypothesis, that can then be investigated in animals.

Pallister-Mosaic syndrome and neuronal migration disorder.

We diagnosed Pallister-Mosaic syndrome (PMS) in a 4-month-old female infant. In addition to the presence of non-specific anomalies, involving anorectal, finger and ear anomalies, characteristic cranio-facial features and irregular skin lesions that appeared after age 2 months suggested the possibility of genetic mosaicism, PMS in particular. Fluorescence in situ hybridization technique revealed an extra copy of chromosome 12p; i (12p) in 30% of cultured skin fibroblasts. When focal skin lesions accompany neurodevelopmental disabilities in early infancy, genetic analysis for mosaicism should be considered for differential diagnosis. Significantly, we describe several phenotypic features and neuroimaging findings of the PMS in the present case, which have not been described in previous reports. The neuroimaging abnormalities we encountered, such as polymicrogyria, speculating congenital brain anomaly, may explain the severe motor and intellectual disabilities of PMS.

Bilateral frontal polymicrogyria and epilepsy in a patient with Turner mosaicism: a case report.

Turner's syndrome (TS) is rarely associated with serious abnormalities of brain structure or malformations of cortical development. We report a 17-year-old girl with TS and 45,XO/46,XX mosaicism presenting bilateral frontal polymicrogyria (BFP) and epilepsy. To our knowledge, the association between TS and BFP has never been reported to date. Our observation confirms that in humans the X-chromosome plays an important role in the development and specialization of brain structure and function. We hypothesize that the absence or abnormalities of developmental genes localized on the X-chromosome could be involved in the pathogenesis of BFP observed in our patient.

Altered glutamate uptake in peripheral tissues from Down syndrome patients.

Overexpression of APP and SOD induces beta-amyloid deposition and oxidative stress in Down syndrome (DS) patients. Both phenomena may impair glutamate transport and decreased glutamate uptake sites have been demonstrated in patient brains at autopsy. Since alterations of APP metabolism and oxidative damage are systemic, we investigated glutamate uptake in platelets and fibroblasts from DS patients to explore whether abnormalities in this process are inherent properties of DS cells and not secondary to neurodegeneration. Glutamate uptake was significantly decreased in platelets (P<0.005 vs. control) and fibroblasts (P<0.001 vs. control) from DS patients, particularly in those with free trisomy and with mitochondrial point mutations. Systemic impairment of glutamate uptake in DS is suggested, probably related to APP overexpression and mitochondrial dysfunction. Such mechanisms may contribute to neurodegeneration and dementia development in these patients.

Mushroom bodies are not required for courtship behavior by normal and sexually mosaic Drosophila.

To elucidate the effect of feminization of male Drosophila brain cells on courtship control, we performed a large scale screening of expression drivers that can suppress male-specific behavior with transformer gene expression. Two drivers caused essentially total courtship suppression. The expression pattern of these drivers did not show any correlation with the mushroom bodies or the antennal lobes, the regions that have been suggested to play important roles in courtship. Ablation of mushroom bodies using hydroxyurea treatment did not affect this courtship suppression. The ablation did not change either wild-type heterosexual behavior or bisexual behavior caused by transformer expression driven by the same drivers used in the previous studies to suggest the involvement of the mushroom bodies in courtship. Our results show that feminization of different nonoverlapping cells in other parts of the protocerebrum was sufficient to cause the same bisexual or suppressed-courtship phenotype. Thus, contrary to previous assumptions, the mushroom bodies are not required for the control of courtship. Present evidence supports its mediation by other distributed protocerebral regions.

The role of X-chromosome inactivation in the manifestation of Rett syndrome.

X-chromosome inactivation (XCI) is random in the majority of patients with classical Rett syndrome (RTT). Preferential inactivation of the X chromosome with the mutated MECP2 gene is found in mildly symptomatic or asymptomatic carrier females. These findings lead to a hypothesis that random XCI is causally involved in the pathogenesis of RTT in heterozygous females. It is the cluster of functionally defective nerve cells lacking fully functional MeCP2 generated by inactivation of normal MECP2 allele that causes the wide spectrum of RTT symptoms. Thus, RTT is a rare human disease manifestation which is triggered most probably by random XCI.

Single cell analysis of CAG repeat in brains of dentatorubral-pallidoluysian atrophy (DRPLA).

Somatic mosaicism of an expanded repeat is present in tissues of patients with triplet repeat diseases. Of the spinocerebellar ataxias associated with triplet repeat expansion, the most prominent heterogeneity of the expanded repeat is seen in dentatorubral-pallidoluysian atrophy (DRPLA). The common feature of this somatic mosaicism is the difference in the repeat numbers found in the cerebellum as compared to other tissues. The expanded allele in the cerebellum shows a smaller degree of expansion. We previously showed by microdissection analysis that the expanded allele in the granular layer in DRPLA cerebellum has less expansion than expanded alleles in the molecular layer and white matter. Whether this feature of lesser expansion in granule cells is common to other types of neurons is yet to be clarified. We used a newly developed excimer laser microdissection system to analyze somatic mosaicism in the brains of two patients, one with early- and another with late-onset DRPLA, and used single cell PCR to observe the cell-to-cell differences in repeat numbers. In the late onset patient, repeat expansion was more prominent in Purkinje cells than in granule cells, but less than that in the glial cells. In the early onset patient, repeat expansion in Purkinje cells was greater than in granule cells but did not differ from that in glial cells. These findings suggest that there is a difference in repeat expansion among neuronal subgroups and that the number of cell division cycles is not the only determinant of somatic mosaicism.

Estimación del riesgo de aneuploidías para los cromosomas sexuales en un paciente 46,XY/47,XXY candidato a fecundación in vitro con microinyección intracitoplasmática espermática / Estimation of risk of aneuploidies for sexual chromosomes in a patient 46,XY/47,XXY candidate for in vitro fertilization by intracytoplasmic sperm injection

Se presenta un embarazo conseguido tras microinyección intracitoplasmática de espermatozoides del eyaculado de un paciente con síndrome de Klinefelter mosaico. El mosaicismo observado en células germinales premeióticas estaba invertido con respecto al observado en sangre periférica. A partir de los estudios meióticos y de hibridación in situ (FISH) en espermatozoides, se estimó que el riesgo genético del paciente para la transmisión de gonosomopatías a la descendencia era equivalente a la de la población control, aconsejándose un ciclo de fecundación in vitro con microinyección intracitoplasmática espermática y posterior diagnóstico prenatal en caso de gestación.Por desgracia, el embarazo no llegó a término. Los pacientes con síndrome de Klinefelter deben ser estudiados con detalle antes de realizar un ciclo de fecundación in vitro con microinyección intracitoplasmática espermática. En estos pacientes se recomiendan los estudios meióticos y de FISH en espermatozoides eyaculados o testiculares, así como diagnóstico prenatal. El diagnóstico genético preimplantacional puede recomendarse sólo en casos de alto riesgo genético. (AU)

Molecular genetic aspects of the phakomatoses: tuberous sclerosis complex and neurofibromatosis 1.

The phakomatoses are a diverse group of diseases characterized by skin lesions in early childhood followed by the development of tumors in many other organs. Tuberous sclerosis complex and neurofibromatosis 1 are of special interest to the neurologist because of their prominent neuro-oncological and neuro-developmental consequences. The cloning of genes responsible for these two diseases has led to the identification of causative mutations, an understanding of basic cellular pathophysiology and the development of animal models. Current laboratory investigations are focused on bringing clinical relevance to these findings, including the prospects of molecular diagnostics and rational therapeutics.

Tandem duplication mosaicism: characterization of a mosaic dup(5q) and review.

Mosaicism for tandem duplications is rare. Most patients reported had abnormal phenotypes of varying severity, depending on the chromosomal imbalance involved and the level of mosaicism. Post-zygotic unequal sister-chromatid exchange has been proposed as the main mechanism for tandem duplication mosaicism. However, previous molecular analyses have implicated both meiotic and post-zygotic origins for the duplication. We describe a newborn male who was originally diagnosed in utero with arrhythmia and tetralogy of Fallot. He had multiple dysmorphic features including telecanthus, blepharophimosis, high broad nasal bridge with a square-shaped nose, flat philtrum, thin upper lip, down-turned corners of the mouth, high-arched palate, micrognathia, asymmetric ears, and long, thin fingers and toes. Karyotyping of peripheral blood lymphocytes showed mosaicism for a tandem duplication of part of the long arm of one chromosome 5: mos46,XY,dup(5)(q13q33)[6]/46,XY[45]. Fibroblast cultures had the same mosaic karyotype with a higher frequency of the dup(5) clone: mos46,XY,dup(5)(q13q33)[9]/46,XY[21]. Fluorescence in situ hybridization analysis with a wcp5 confirmed the chromosome 5 origin of the additional material. Parental karyotypes were normal indicating a de novo origin of the dup(5) in the proband. Molecular analyses of chromosome 5 sequence-tagged-site (STS) markers in our family were consistent with a post-zygotic origin for the duplication. Therefore, mosaicism for tandem duplications can arise both through meiotic or mitotic errors, as a result of unequal crossing over or unequal sister-chromatid exchange, respectively. Our review indicates that mosaicism for tandem duplications is likely under-ascertained and that parental karyotyping of probands with non-mosaic tandem duplications should be performed.

Cell mosaic patterns in the native and regenerated inner retina of zebrafish: implications for retinal assembly.

In part because of its laminar organization and morphologically distinct cell populations, the vertebrate retina has often been used as a system for investigating the assembly of neural structures. The retinas of adult teleost fish, because they grow throughout life and can regenerate following an injury, provide an especially attractive model system for such investigations. In an effort to provide a quantitative foundation for testing hypotheses regarding the mechanisms of pattern formation during growth and regeneration of the vertebrate retina, nearest neighbor and auto-correlation analyses were used to examine the mosaic patterns of eight inner retinal cell groups in the native and regenerated retina of adult zebrafish. In both native and regenerated retina, the mosaic patterns of most inner retinal cells are non-random. However, regenerated mosaics tend toward significantly lower nearest neighbor distances, less orderly patterns, and more variable radial locations than their native retina counterparts. The individual cell groups in both native and regenerated inner retina are likely to be spatially distributed independently. The results support the hypotheses that, in the adult zebrafish: 1) distinct inner retinal cell groups of native retina are also present in regenerated retina; 2) the assembly of inner retinal cell mosaics is controlled by non-random spatial organizing mechanisms during development, growth, and regeneration; and 3) the spatial organization of cell mosaics is disrupted during regeneration. The results suggest that retinal regeneration may represent a spatially disrupted recapitulation of retinal developmental mechanisms.

Direct androgenic regulation of calcitonin gene-related peptide expression in motoneurons of rats with mosaic androgen insensitivity.

The spinal nucleus of the bulbocavernosus (SNB) and its target muscles, bulbocavernosus and levator ani (BC/LA), form a sexually dimorphic neuromuscular circuit whose development and maintenance are androgen-dependent. The mechanisms whereby androgen regulates gene expression in the SNB of adult rats are largely unknown, although a retrograde influence from the BC/LA muscles has been suggested to underlie the suppression of calcitonin gene-related peptide (CGRP) expression observed in SNB motoneurons after systemic androgen treatment. A mosaic paradigm was used to determine the site of action of androgen in the regulation of CGRP expression in SNB motoneurons. As a consequence of random X chromosome inactivation, androgenized female rats heterozygous for the tfm androgen receptor (AR) mutation (XwtXtfm-mosaics) express a mosaic of androgen-sensitive and androgen-insensitive motoneurons in the SNB, whereas the BC/LA target musculature appears to be uniformly sensitive to androgens. In adult mosaics, testosterone administration resulted in a reduction in the proportion of androgen-sensitive cells expressing CGRP, whereas no such reduction was observed in the androgen-insensitive population, indicating that neuronal AR plays an essential role in the neuromuscular regulation of CGRP expression in these motoneurons. This provides the first in vivo demonstration of AR regulation of gene expression unambiguously localized to a neuronal population.

Focal hippocampal gain of NGF function elicits specific septal cholinergic reorganization.

The influence of NGF on the neuroanatomic substrate(s) subserving learning and memory was probed by somatic mosaic analysis. NGF XAT mice underwent unilateral hippocampal delivery of virus vector expressing cre recombinase to produce focal NGF gain of function mosaics. Activated mice expressing increased NGF, but not control mice transduced with the lacZ gene showed reorganization of the septohippocampal projection assessed by retrograde labeling with Fluorogold (FG). Mice mosaic for NGF function demonstrated in ipsilateral medial septum and diagonal band significant increases in FG-labeled cell bodies (94%), ChAT-labeled cells (55%), double-positive cells (190%) and increased somal size of double-positive cells (56%) than did non-activated mice. These results indicate that reorganization of the cholinergic septal input to a specific hippocampal region is promoted by gain of NGF function.

Ring chromosome 14 complicated with complex partial seizures and hypoplastic corpus callosum.

A Japanese male with mosaicism of ring chromosome 14 and chromosome 14 monosomy is described. He demonstrated the characteristic morphologic features of ring chromosome 14, in addition to mental retardation and epileptic seizures. Clusters of complex partial seizures, one of which originated in the left frontocentral region on electroencephalographic monitoring, were evident. His seizures responded to phenobarbital, and his mental and motor development was only mildly retarded. Magnetic resonance imaging revealed a hypoplastic corpus callosum, previously unknown in association with this syndrome.