PCR-PRINS-FISH analysis of structurally abnormal sex chromosomes in eight patients with Turner phenotype

According to cytogenetic analysis, about 50% of Turner individuals are 45,X. The remaining cases have a structurally abnormal X chromosome or are mosaics with a second cell line containing a normal or abnormal sex chromosome. In these mosaics, approximately 20% have a sex marker chromosome whose identity cannot usually be determined by classical cytogenetic methods, requiring the use of molecular techniques. Polymerase chain reaction (PCR), primed in situ labeling (PRINS), and fluorescence in situ hybridization (FISH) analyses were performed in 8 patients with Turner syndrome and 45,X mosaic karyotypes to determine the origin and structure of the marker chromosome in the second cell line. Our data showed that markers were Y-derived in 2 patients and X-derived in the remaining 6 patients. We were also able to determine the breakpoints in the two Y chromosomes. The use of cytogenetic and molecular techniques allowed us to establish unequivocally the origin, X or Y, of the marker chromosomes in the 8 patients with Turner phenotype. This study illustrates the power of resolution and utility of combined cytogenetic and molecular approaches in some clinical cases.

Mutations in Kir2.1 Cause the Developmental and Episodic Electrical Phenotypes of Andersen's Syndrome

Andersen's syndrome is characterized by periodic paralysis, cardiac arrhythmias, and dysmorphic features. We have mapped an Andersen's locus to chromosome 17q23 near the inward rectifying potassium channel gene KCNJ2. A missense mutation in KCNJ2 (encoding D71V) was identified in the linked family. Eight additional mutations were identified in unrelated patients. Expression of two of these mutations in Xenopus oocytes revealed loss of function and a dominant negative effect in Kir2.1 current as assayed by voltage-clamp. We conclude that mutations in Kir2.1 cause Andersen's syndrome. These findings suggest that Kir2.1 plays an important role in developmental signaling in addition to its previously recognized function in controlling cell excitability in skeletal muscle and heart.

Blepharo-cheilo-dontic (BCD) syndrome in two Mexican patients

The combination of lagophthalmia, ectropion of the lower eyelids, distichiasis, euryblepharon, cleft lip/palate, and oligodontia was recently named blepharo-cheilo-dontic (BCD) syndrome. Different combinations of these signs have been found sporadically, with autosomal dominant inheritance. Ectropion of the lower eyelids, lagophthalmia, and bilateral cleft lip/palate appear to be the more common manifestations. We report on two unrelated patients with bilateral cleft lip/palate and lagophthalmia. One of these two patients had familial cleft lip/palate in two generations, probably as a variable expression of an autosomal dominant gene.

Andersen syndrome autosomal dominant in three generations

Andersen syndrome is a rare entity and comprises potassium sensitive periodic paralysis, ventricular arrhythmia, and an unusual facial appearance; syncope and sudden death have also been reported. The recognition of the characteristic face permits an early diagnosis in order to detect the severe systemic manifestations that are associated with this syndrome. The genetic defect is not linked to any other form of potassium sensitive periodic paralysis nor is it related to that of the long QT syndrome; nevertheless, a prolonged QT interval can be detected in a significant proportion of the cases. Sixteen cases of this syndrome have been described. We report on a three-generation family with 10 affected members. To our knowledge, this is the largest number of cases reported in one family. We noted some additional minor anomalies such as broad forehead and malar hypoplasia. Our patients had variable expression in the classical triad and of the severity of the systemic manifestations. Five of 8 affected studied members did not have a long QTc, which has been suggested as a constant finding in this syndrome.

Combined trisomy 9 and Ullrich-Turner syndrome in a girl with a 46,X,der(9)t(X;9)(q12;q32) karyotype

Total trisomy 9 is a rare disorder with most patients dying before age 4 months. Herein, we report a 9-year-old girl with mental retardation, short stature, a peculiar face and other minor defects, who was diagnosed as having an unbalanced de novo X-autosome translocation with a 46,X,der(9)t(X;9)(q12;q32) karyotype resulting in almost a full trisomy 9(pter-->q32) and a partial monosomy X(q12-->pter). The clinical findings of our patient, almost exclusively resemble those of trisomy 9p and the Ullrich-Turner syndromes and has few manifestations of 9q trisomy. BrdU replication studies by Giemsa staining showed an earlier replication of 9p in the translocated chromosome, but a marked late-replication pattern for almost the complete 9q arm involved in the translocation. FISH studies confirmed the presence of three 9 centromeres, excluded the presence of the X centromere signal in the rearranged chromosome, and showed that both Xq telomeric sequences were present. BrdU replication studies by FISH showed an usual pattern of striking late-replication around the XIC of the derivative chromosome, but early replication of the chromosome 9p segment and distal Xq.

Molecular analysis of mosaicism for two different de novo acrocentric rearrangements demonstrates diversity in Robertsonian translocation formation

Robertsonian translocations (ROBs) involving chromosome 21 occur in about 5% of individuals with Down syndrome. ROBs are the most common chromosomal rearrangements in humans and are formed through whole arm exchanges of any two acrocentric chromosomes. The de novo formation of ROBs occurs at exceptionally high rates. The present case concerns a child with mosaic Down syndrome who has two cell lines that contain two different de novo ROBs: 45,XX,rob(14;21)(q10;q10) and 46,XX,rea(21;21)(q10;q10),+21. To elucidate the mechanisms by which the rearrangements formed, somatic cell hybrids were constructed to allow the parental origins of the chromosomes involved in the ROBs to be distinguished. The analysis of the hybrids showed that the rob(14q21q) must have formed postzygotically because it contained a maternal chromosome 14 and a paternal chromosome 21. Furthermore, hybrid analysis of the rea(21q21q) demonstrated two copies of the same chromosome from the mother and thus, by definition, was an isochromosome [i(21q)]. All free-lying chromosomes 21 isolated in hybrids were of maternal origin. These chromosomes may have originated from either of the patient's cell lines. We present four hypotheses for the formation of the two cell lines of this child. This case is part of an ongoing project to determine the mechanism(s) of de novo ROB formation and the results differ from the other de novo rob(14q21q) studied in our laboratory (n = 7) in that all previously studied translocations were maternally derived, leading to the conclusion that most de novo rob(14q21q) occur in oogenesis. The current case illustrates that other mechanisms may contribute to ROB formation.

Analysis of the human Sonic Hedgehog coding and promoter regions in sacral agenesis, triphalangeal thumb, and mirror polydactyly

The human Sonic Hedgehog gene (SHH) is one of the vertebrate homologs related to the Drosophila segment polarity gene hedgehog. The entire coding and promoter region of the SHH gene, including 2 kb 5' of the transcriptional start site has been screened for mutations in families with autosomal dominant sacral agenesis and autosomal dominant triphalangeal thumb, two conditions previously known to be linked to 7q36. We have also studied the SHH gene in five families with mirror polydactyly associated with tibial hemimelia and in 51 unrelated patients with neural tube defects. Except for two sequence variants in exon 3, no mutations were found in these disease categories. OFF

[Epilepsy and pregnancy. Risks and benefits of anticonvulsant treatment]

Epilepsy is the most frequent neurological disorder during pregnancy. Potential adverse actions of anticonvulsant drugs of fetal development are one of the main concerns of practitioners. In this paper we investigated the pregnancy complications and teratogenic effects of several anticonvulsant agents in 50 epileptic women and their newborns delivered at "Dr. Manuel Gea González" SSA General Hospital, among 1989 and 1992. A large number of these patients (78%) were treated with carbamazepine or phenytoin and 10% needed combined anticonvulsant therapy. Most had a normal vaginal delivery (76%) and only in 3 cases (6%) minor birth defects were observed. These anomalies included distal digital hypoplasia and ear flap abnormalities. Our results suggest that anticonvulsant drugs induce a few maternal and obstetric complications and have a moderate teratogenic risk, particularly seizures can be controlled by using a single antiepileptic drug.

Idiopathic multicentric osteolysis with facial anomalies and nephropathy

Idiopathic osteolysis denotes a group of rare bone disorders differentiated on the basis of clinical, radiological, and genetic criteria. Idiopathic multicentric osteolysis (IMO) is one form of osteolysis that can occur as an autosomal dominant condition. In childhood, affected individuals have arthritic-like episodes, followed by progressive deformities, radiological osteolytic changes, and variable degrees of disability. A peculiar face and variable renal involvement have been described as associated manifestations. We report on a family with three members affected by IMO in two generations showing variable bone changes and persistent proteinuria. A sporadic case with severe renal damage is also described in which a de novo dominant mutation is suggested. All patients had peculiar facial manifestations including triangular shape, protruding eyes, and micrognathia. These manifestations may be part of the syndrome of IMO.

Absent tibiae, triphalangeal thumbs and polydactyly: description of a family and prenatal diagnosis

A family with absent tibiae, triphalangeal thumbs and polydactyly is described. Bilateral absence of tibiae is the most severe manifestation of this syndrome. The pedigree of this family suggests an autosomal dominant inheritance with variable expression. Prenatal diagnosis was made at 20.5 weeks of pregnancy. Fetal radiographs showed the presence of both tibiae; this finding was confirmed at birth.

Variability between and within laboratories in the analysis of structural chromosomal abnormalities

The frequency of structural chromosomal aberrations in two samples (AM and PM of the same day) from each of nine normal subjects, cultured in two different laboratories, was studied by six observers. The results were analyzed in order to determine the relative importance of inter- and intralaboratory factors in the variability of chromosomal abnormalities. In addition to the difference in the frequency of the abnormalities between the subjects studied, there were differences due to observers from different laboratories (P less than 0.01), as well as between laboratories (P less than 0.01). These results could be explained in part by insufficient agreement between observers from different laboratories and by differences in the quality of the method used.