Genital lentigines in a 6-year-old boy with a family history of Cowden's disease: clinical and genetic evidence of the linkage between Bannayan-Riley-Ruvacalba syndrome and Cowden's disease

BACKGROUND

In 1997, it was reported that a PTEN gene deletion, a common genetic mutation in Cowden's disease (CD), was identified in a patient with Bannayan-Riley-Ruvacalba (BRR), suggesting that the two diseases were allelic. However, the clinical overlap between the two diseases has largely remained unclear.

OBJECTIVE

To confirm the genetic and clinical association in a family segregating both CD and BRR.

METHODS

Clinical evaluation and genetic analysis using a denaturing gradient gel electrophoresis (DGGE), temporal temperature gradient electrophoresis (TTGE), and DNA sequencing techniques.

RESULTS

Our patient presents with typical BRR clinical manifestations, including multiple lentigines on his penis, while his mother presents with typical manifestations of CD, including multiple malignancies. Genetic analyses of leukocytes from the patient and his mother showed mutations in exon 8 that was identified as the presumably truncating mutation R335X.

CONCLUSION

This report provides clinical evidence that both BRR and CD are closely related and confirms the PTEN gene mutation in BRR and CD patients segregating in the same family, thus confirming the genetic linkage between the two genodermatoses.

Prenatal molecular cytogenetic diagnosis of partial tetrasomy 10p due to neocentromere formation in an inversion duplication analphoid marker chromosome

Neocentromeres are fully functional centromeres found on rearranged or marker chromosomes that have separated from endogenous centromeres. Neocentromeres often result in partial tri- or tetrasomy because their formation confers mitotic stability to acentric chromosome fragments that would normally be lost. We describe the prenatal identification and characterization of a de novo supernumerary marker chromosome (SMC) containing a neocentromere in a 20-wk fetus by the combined use of comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). GTG-banding of fetal metaphases revealed a 47,XY,+mar karyotype in 100% of cultured amniocytes; parental karyotypes were both normal. Although sequential tricolor FISH using chromosome-specific painting probes identified a chromosome 10 origin of the marker, a complete panel of chromosome-specific centromeric satellite DNA probes failed to hybridize to any portion of the marker. The presence of a neocentromere on the marker chromosome was confirmed by the absence of hybridization of an all-human-centromere alpha-satellite DNA probe, which hybridizes to all normal centromeres, and the presence of centromere protein (CENP)-C, which is associated specifically with active kinetochores. Based on CGH analysis and FISH with a chromosome 10p subtelomeric probe, the marker was found to be an inversion duplication of the distal portion of chromosome 10p. Thus, the proband's karyotype was 47,XY,+inv dup(10)(pter-->p14 approximately 15::p14 approximately 15-->neo-->pter), which is the first report of partial tetrasomy 10p resulting from an analphoid marker chromosome with a neocentromere. This study illustrates the use of several molecular strategies in distinguishing centric alphoid markers from neocentric analphoid markers.

Jumping translocations in spontaneous abortions

Chromosome translocations involving one donor chromosome and multiple recipient chromosomes have been referred to as jumping translocations (JTs). Acquired JTs are commonly observed in cancer patients, mainly involving chromosome 1. Constitutional forms of JTs mostly involve the acrocentric chromosomes and their satellites and have been reported in patients with clinical abnormalities. Recognizable phenotypes resulting from these events have included Down, Prader-Willi, and DiGeorge syndromes. The presence of JTs in spontaneous abortions has not been previously described. The breakpoints of all JTs occur in areas rich in repetitive DNA (telomeric, centromeric, and nucleolus organizing regions). We report two different unstable chromosome rearrangements in samples derived from spontaneous abortions. The first case involved a chromosome 15 donor. The recipient chromosomes were 1, 9, 15, and 21, and the respective breakpoints were in either the heterochromatic regions or the centromeres. FISH studies confirmed that the breakpoints of the jumping 15 rearrangement did not involve the Prader-Willi region but originated at the centromere or in the proximal short arm. A second case of instability was observed with a rearrangement resulting from a presumed de novo 8;21 translocation. Three JT cell lines were observed. They consisted of a deleted 8p chromosome, a dicentric 8;21 translocation, and an 8q isochromosome. The instability regions appeared to be at the pericentromeric region of chromosome 8 and the satellite region of chromosome 21. Both cases proved to be de novo events. The unstable nature of the JT resulting in chromosomal imbalance most likely contributed to the fetal loss. It appears that JT events may predispose to chromosomal imbalance via nondisjunction and chromosomal rearrangement and, therefore, may be an unrecognized cause of fetal loss.

Clinical applications of comparative genomic hybridization

PURPOSE

Comparative genomic hybridization (CGH) is a powerful DNA-based cytogenetic technique that allows the entire genome to be scanned for chromosomal imbalances without requiring the sample material to be mitotically active. During the past 2 years we received many requests from various medical centers around the country to use CGH to resolve the identity of aberrant chromosomal material.

METHODS

We report the use of CGH for the evaluation of 12 clinical postnatal cases in which traditional cytogenetic analysis yielded ambiguous results. This series consisted of five marker chromosomes, five unbalanced translocations, and two intrachromosomal duplications.

RESULTS

Identification and characterization of the additional unknown chromosomal material was achieved with use of CGH. All CGH findings were validated by traditional fluorescence in situ hybridization and other specialized staining techniques. CONCLUSLONS: These results demonstrate the effective use of CGH as a focused, single-step method for the identification of chromosomal material of unknown origin.

Monosomy 5 in acute megakaryoblastic leukemia. Report of two cases

Two cases of acute megakaryoblastic leukemia are reported. The diagnoses were confirmed by clinical, morphologic, and cytochemical analysis. Karyotypic analysis demonstrated monosomy 5 in both patients, providing further evidence that acute megakaryoblastic leukemia is a subset of the acute nonlymphocytic leukemias and may be etiologically related to the myelodysplastic syndromes.

Pseudomosaicism for trisomy 13. Three case reports

Pseudomosaicism is of particular concern in prenatal diagnosis when it involves mosaicism for a cytogenetic abnormality associated with a clinical syndrome which is compatible with postnatal life, such as trisomies for chromosomes 13, 18, and 21. The lack of data regarding the outcome of pregnancies involving these specific kinds of pseudomosaicism makes genetic counselling difficult. Three cases of prenatal diagnosis of pseudomosaicism for trisomy 13, each of which had a normal outcome, will be presented (Tables 1 and 2). The three main areas for consideration are: (1) the genetic counselling issues, (2) the additional prenatal diagnostic options available to evaluate the status of the fetus in an attempt to identify some of the clinical features of trisomy 13, and (3) the outcome of the pregnancies.

Characterization of the supernumerary chromosome in cat eye syndrome

Most individuals with cat eye syndrome (CES) have a supernumerary bisatellited chromosome which, on the basis of cytogenetic evidence, has been reported to originate from either chromosome 13 or 22. To resolve this question, a single-copy DNA probe, D22S9, was isolated and localized to 22q11 by in situ hybridization to metaphase chromosomes. The number of copies of this sequence was determined in CES patients by means of Southern blots and densitometry analysis of autoradiographs. In patients with the supernumerary chromosome, four copies were found, whereas in one patient with a duplication of part of chromosome 22, there were three copies. Therefore, the syndrome results from the presence of either three or four copies of DNA sequences from 22q11; there is no evidence that sequences from other chromosomes are involved. This work demonstrates how DNA sequence dosage analysis can be used to study genetic disorders that are not readily amenable to standard cytogenetic analysis.

Distal 15q trisomy: phenotypic comparison of nine cases in an extended family

Nine related individuals have been identified as being trisomic for the distal part of the long arm of chromosome 15 (15q23 to 15qter). The physical characteristics, especially the facial features, of these nine cases are similar and distinctive. These include: facial asymmetry, down-slanting palpebral fissures, ptosis, prominent nose, long philtrum, down-turned mouth, midline crease in the lower lip, puffy cheeks, and micrognathia. By comparing related individuals with the same translocation, the variability due to different breakpoints can be eliminated. Clinical similarities between unrelated individuals with similar duplicated 15q material, but differing second chromosomes, suggest that the phenotype is due to the extra distal 15q chromosomal material. We conclude that distal 15q trisomy produces a clinically recognizable syndrome.

Acquired idiopathic sideroblastic anemia: a new chromosomal abnormality

We describe two patients with acquired idiopathic sideroblastic anemia and a terminal deletion of chromosome No. 11. In spite of the marked chromosomal abnormality neither patient has developed acute leukemia.

Cytogenetic findings in the dysmyelopoietic syndrome

Cytogenetic studies of bone marrow specimens from 15 patients with dysmyelopoietic syndrome are presented. The group consists of nine patients with refractory anemia with excess of blasts (RAEB), three patients with chronic myelomonocytic leukemia (CMMoL), and three patients with acquired idiopathic sideroblastic anemia (AISA). None of these patients had a prior history of therapeutic or occupational exposure to potential carcinogenic agents, G(TG)-banding revealed clonal abnormalities in nine of the 15 patients. Five of these patients exhibited one or more of the following cytogenetic abnormalities: 5q deletion, -7, +8, or +21. The AISA group appeared to be unique as chromosome abnormalities were seen in two of the three patients and the clinical course in these patients had been prolonged without progression to acute leukemia. No other clinical correlation could be made in the blast RAEB and CMMoL groups, except for possible survival benefit in patients with normal karyotypes.

Burkitt's leukemia: a re-evaluation

Two patients who presented with acute leukemia of Burkitt's cell type are discussed. Although one patient died within four months of diagnosis, the other has maintained a one year clinical complete remission. The clinical and morphologic picture of Burkitt's leukemia is nonspecific and therefore requires complementary studies including cytochemistry, transmission electron microscopy, cell surface markers and cytogenetics studies to establish diagnosis. Serial bone marrow aspirations with marker analyses may detect relapse at an earlier stage than conventional cytology, allowing therapy to be modified prior to overt clinical relapse.

Association of monosomy 7 with myelodysplasia following chemotherapy for Hodgkin's disease: serial observations

Myelodysplasia and acute nonlymphocytic leukemia following therapy for Hodgkin's disease are observed rather frequently. Herein, we describe a patient with this syndrome treated with prolonged chemotherapy (alone), having a monosomy 7 karyotype. Cytogenetic studies were performed serially during the myelodysplasia preceding overt leukemia. Review of the literature and relevance of these findings are discussed.