A new case of rearrangement of chromosome 15 associated with Prader Willi syndrome

Sudden cardiac death in a child affected by Prader-Willi syndrome

A case of sudden cardiac death in a 3-year-old young male affected by Prader-Willi syndrome, clinically diagnosed and confirmed by means of DNA methylation, is presented. The infant suddenly collapsed at home and was taken apparently unconsciousness by his mother to the emergency clinic where he was pronounced dead. A complete postmortem examination was performed and the histological findings led to the definition of cardiac death with a typical picture of contraction band necrosis. Pulmonary hypoxic alterations are frequently reported as the primary cause of death in PWS cases. In this fatal case according to the macroscopic and microscopic findings, the cause of death was most likely cardiac and possibly related to contraction band necrosis linked with ventricular fibrillation and sudden death.

Nonreciprocal and jumping translocations of 15q1----qter in Prader-Willi syndrome

We analyzed 33 cases of Prader-Willi syndrome (PWS) (including 2 personal observations) with translocations of 15q1----qter onto the terminals of different, apparently whole chromosomes. In all but one of the 23 informative cases the translocations was de novo. Thirty of the patients were unbalanced and 27 had a 45-chromosome constitution compatible with a 3:1 segregation. One balanced and 2 unbalanced translocations were jumping ones. The possible existence of actual non-reciprocal translocations in man is indicated by the following considerations about these and other PWS-associated rearrangements: 1) The observed excess of de novo translocations; 2) the relatively frequent familial occurrence of reciprocal 15q translocations; 3) the concurrence in 3 terminal translocation cases of an idic (15); 4) the visualization of jumping terminal translocations as simple transpositions rather than as successive reciprocal exchanges; 5) the predominance of true isodicentrics in PWS patients with extra inv dup(15) chromosomes; and 6) the rarity of extra derivatives resulting in 15q proximal tertiary trisomy. Additional findings in the present series were normal parental age in the de novo 45-chromosome cases, an apparently random distribution of telomeric breakpoints, and the occurrence of different breakpoints within the 15q1 region.

Prader-Willi syndrome: current understanding of cause and diagnosis

Prader-Willi syndrome (PWS) is characterized by hypotonia, obesity, hypogonadism, short stature, small hands and feet, mental deficiency, a characteristic face, and an interstitial deletion of the proximal long arm of chromosome 15 in about one-half of the patients. The incidence is estimated to be about 1 in 25,000, and PWS is the most common syndromal cause of human obesity. DNA abnormalities, usually deletions or duplications of chromosome 15, have been identified in individuals with PWS with or without recognizable chromosome 15 deletions. Paternal origin of the chromosome 15 deletion by cytogenetic and DNA studies has been found in nearly all PWS individuals studied. No cytogenetic evidence for chromosome breakage has been identified, although an environmental cause (e.g., paternal hydrocarbon-exposed occupations) of the chromosome 15 abnormality has been proposed. PWS patients with the chromosome 15 deletion are more prone to hypopigmentation compared with PWS individuals with normal chromosomes, but no other clinical differences are consistently identified between those with and without the chromosome deletion. Anthropometric, dermatoglyphic, and other clinical findings indicate homogeneity of PWS patients with the chromosome deletion and heterogeneity of the nondeletion patients. A review of our current understanding of the major clinical, cytogenetic, and DNA findings is presented, and clinical manifestations and cytogenetic abnormalities are summarized from the literature.

Familial marker chromosome due to 3:1 disjunction of t(9;15) in a grandparent

An extra small chromosome detected in amniotic fluid was identified as the product of a translocation [46,XX,t(9;15)(p24;q11.2)]. This case is unusual in that individuals with the unbalanced karyotype resulting from a 3:1 disjunction are phenotypically normal.

Classification and evaluation of the obesities

Obesity is a condition of multifactorial etiology that can be associated with important health and functional consequences. Suggestions for the proper evaluation of obese patients have been presented along with brief descriptions of the rationales for their use. The evaluation protocol has been summarized in two algorithms to aid in the performance of a complete and organized work-up.

Deletions of proximal 15q and non-classical Prader-Willi syndrome phenotypes

A deletion of the long arm of chromosome 15 (usually involving bands 15q11-q12) has been seen in approximately 50% of Prader-Willi syndrome (PWS) patients [Ledbetter et al, 1982]. However, 14 patients with non-PWS (or atypical PWS) phenotype with 15q deletion indicate great clinical variability. A deletion was found in a propositus with a de novo translocation [45,XY, -15, -22, +rec(15;22) (22pter----22q13.2::15q14----15qter)], who had anomalies not normally observed in PWS patients. Activities of several enzymes mapped to the involved chromosomes were studied in the patient and control individuals. A 50% decrease in the level of arylsulfatase-A confirmed a small deletion in 22q(22q13.2----qter), and additional studies localized more precisely the loci for alpha-mannosidase (cytoplasmic) and beta-galactosidase.

Unbalanced reciprocal translocations in cases of Prader-Willi syndrome

A case of Prader-Willi syndrome (PWS) associated with a de novo unbalanced 15q;17q reciprocal translocation presumptively resulting from the tertiary monosomic form of 3:1 meiotic disjunction is described. Twenty-three similar unbalanced translocations have been identified from the literature. The 24 karyotypes are characterised by having 45 chromosomes, monosomy for the pericentromeric region of chromosome 15 (range pter----q11 to q21), and little monosomy of the recipient (non-15) chromosome. Two-thirds of the cases with these karyotypes have phenotypic features of PWS. It seems probable that (i) where unbalanced reciprocal translocations are associated with PWS, they will almost invariably be presumptive segregants of the tertiary monosomic form of 3:1 disjunction and (ii) the majority of cases found with this type of karyotype, particularly it appears when de novo in origin, will be associated with phenotypic features of PWS.

Chromosome 15 anomalies and the Prader-Willi syndrome: cytogenetic analysis

The behaviour of chromosome 15 is very different from that of the other acrocentric chromosomes. The cytogenetic characteristics of rearrangements associated with Prader-Willi syndrome (PWS) are analyzed as similar rearrangements irrespective of the associated phenotype (reciprocal translocations of chromosome 15, small bisatellited additional chromosomes, Robertsonian translocations, interstitial deletions, pericentric inversions). This study suggests that: (1) The proximal ( 15q ) region and PWS seem to be indissociable ; (2) chromosome 15 has an indisputable cytogenetic originality which could be related to its histochemical properties. Chromosome 15 constitutive heterochromatin usually contains much 5-methylcytosine-rich DNA and a large amount of each of the four satellite DNAs. Furthermore the existence in the proximal ( 15q ) region of one or several palindromic sequences could be postulated to explain the great lability of this region of chromosome 15.

Prader-Willi syndrome associated with inversion of chromosome 15

A boy with Prader-Willi syndrome was found to have an inversion of chromosome 15,[46,XY,inv(15)(p13q13)]. His unaffected father has an apparently identical inversion of chromosome 15 but in addition has a number 14 chromosome with double satellites. This report supports previous indications of a relationship between a "position effect" and the etiology of Prader-Willi syndrome. However, a more complicated explanation is required in view of the cytogenetic findings in the proband's father.

Prader-Willi syndrome and chromosome 15. A clinical discussion of 20 cases

A chromosome 15 anomaly was observed in 12 of 20 patients, 17 of whom were clinically suspected of having Prader-Willi syndrome (PWS). The clinical features of eight cases with 15q11-12 deletion were very similar to those originally described in PWS. On the other hand, the group of normal karyotype patients is heterogeneous, and their features do not strictly correspond to the clinical definition of PWS. However, the hypothesis that PWS is associated with deletion of 15q11-12 can neither explain the apparently balanced translocations of chromosome 15 nor account for the small supernumerary metacentric chromosomes corresponding to an isochromosome 15 for band 15q11 observed in some cases.

Translocations in Prader-Willi syndrome

The Prader-Willi Syndrome (PWS) has frequently been associated with chromosomal anomalies involving the region 15q11-q12. The first case of this syndrome associated with a de novo translocation involving chromosomes 11 and 15 is reported. The breakpoints were identified as 11q25 and 15q11 or q12[45, XX,t(11;15)(q25;q11-12)], resulting in the deletion of 15pter leads to 15q11-q12. Previously reported cases of PWS associated with translocations are reviewed in relation to the "deletion hypothesis."

The cytogenetic controversy in the Prader-Labhart-Willi syndrome

A patient with Prader-Labhart-Willi syndrome (PLWS) was found to have mosaic partial trisomy 15: 46,XY/47,XY, + del(15) (pter leads to q1.3:) in both lymphocytes and fibroblasts. Thus, another novel aberration is added to the spectrum of chromosome abnormalities seen in this syndrome. The spectrum includes deletion of the short arm of chromosome 15, interstitial deletion of 15q1.2, inverted duplication of 15p (tetrasomy 15p), partial trisomy 15 different from that encountered in this patient, and a variety of aberrations involving other chromosomes. A hypothesis that the chromosome aberrations are due to a presumed gene for the PLWS may have merit and could be tested in the laboratory by exposing chromosomes of patients with PLWS to mutagens to search for secondary chromosome derangements.

Recurrent spontaneous abortions due to a homologous Robertsonian translocation (14q14q)

A female with a history of recurrent spontaneous abortions was shown to carry a balanced Robertsonian translocation involving the No 14 homologues. One abortus had trisomy 14 with a 46,XX,-14,+t(14q14q)mat karyotype.

Adjacent 2 meiotic disjunction. report of a case resulting from a familial 13q;15q balanced reciprocal translocation and review of the literature

An abnormal short-lived female infant with almost complete trisomy 13 (pter leads to q32 or 33) and partial monosomy 15 (pter leads to q14 or 15) resulting from an adjacent 2 meiotic disjunction of a paternal reciprocal translocation is described. Cases with monosomy of chromosome 15 material are reviewed. It appears likely that monosomy of an interstitial long arm segment, approximating to 15q21 leads to 24, imparts the lethality associated with the full monosomic condition. Adjacent 2 disjunction in man has been further characterised by reviewing the literature.

The usefulness of NOR and RFA banding in prenatal diagnosis: a case report

Prenatal chromosome analysis of amniotic cells showed a male fetus to carry an unusual marker D chromosome containing extra genetic material on the short arm, which could be interpreted as a possible t(D;G) or t(D;Fq) unbalanced translocation using non-branded preparations or a routine GTG band method. Analysis of this marker by NOR and RFA banding and parental chromosome studies showed the marker to be an unusual variant of the satellited area of chromosome 15, with no associated phenotypic anomalies. The usefulness of NOR and RFA banding as aids in chromosome identification in prenatal diagnosis is discussed.