[Observation of the 13-15 chromosome group in a ring (46,XY,15r)]

Ring chromosome 15 - cytogenetics and mapping arrays: a case report and review of the literature

BACKGROUND

Ring chromosome 15 has been associated in previous studies with different clinical characteristic such as cardiac problems, digit and musculoskeletal abnormalities, and mental and motor problems among others. Only 97 clinical cases of ring chromosome 15 syndrome have been reported since 1966 and a common phenotype for these patients has not been established.

CASE PRESENTATION

The present case report describes a 15-month-old girl from the Amazon region of Ecuador, of Mestizo ancestry, who after cytogenetic tests showed a 46,XX,r(15) karyotype in more than 70% of metaphases observed. Her parents were healthy and non-related. The pregnancy was complicated and was positive for intrauterine growth retardation. Her birth weight was 1950 g, her length was 43.5 cm, and she had a head circumference of 29.3. In addition to postnatal growth delay, she had scant frontal hair, small eyes, hypertelorism, low-set of ears, flattened nasal bridge, anteverted nostrils, down-turned mouth, three café au lait spots, and delayed dentition.

CONCLUSIONS

Despite the frequency of some phenotypes expressed in the different clinical cases reviewed and the present case, a common phenotype for patients with ring 15 could not be determined and it is restricted to the region of the chromosome lost during the ring formation.

Two patients with ring chromosome 15 syndrome

We report on 2 patients (3 1/2 year-old-male and 6-year-old female) with the ring 15 chromosome syndrome and speech delays and review 25 cases from the literature. The main characteristics of this syndrome include growth retardation (100%), variable mental retardation (95%), microcephaly (88%), hypertelorism (46%), and triangular facies (42%). Other frequent findings include delayed bone age (75%), brachydactyly (44%), speech delay (39%), frontal bossing (36%), anomalous ears (30%), café-au-lait spots (30%), cryptorchidism (30%), and cardiac abnormalities (30%). The average age at diagnosis was 8.1 years. The average maternal and paternal age at the time of birth was 28 and 31 years, respectively.

Severe growth failure associated with atrophic intestinal mucosa and ring chromosome 15

Ring chromosome 15 was detected in a boy with severe growth failure and no dysmorphic features who had previously been found to have an atrophic intestinal mucosa, a finding not observed in about 300 patients with ring autosome reported so far. Of the 137 metaphases examined, 8.1% had secondary aneuploidy produced by the structural and behavioural instability of the ring. Ring derivatives could also be seen in lymphocytes after only one cycle in the culture, indicating that such cells are also generated in vivo. We observed an increased cell death rate in fibroblast culture by Trypan Blue exclusion. These results suggest that there is a continuous in vivo generation of cells with increased mortality resulting in both growth failure and atrophic intestinal mucosa in the patient. The atrophic intestinal mucosa might be a manifestation of ring instability.

Phenotypic delineation of ring chromosome 15 and Russell-Silver syndromes

A male child with features of the Russell-Silver syndrome, including pre- and postnatal growth delay, triangular facies, bilateral fifth finger clinodactyly, and disproportionate lower extremities, was found to have a ring chromosome 15 in all peripheral leucocytes examined. Review of the reported cases of ring chromosome 15 defines a malformation syndrome with a characteristic facies related to deletion of the 15q26.2----qter region. Russell-Silver and ring 15 syndromes share clinical features such as growth deficiency, triangular facies, digital anomalies, and café-au-lait spots. Microcephaly, mental retardation, facial dysmorphology, limb anomalies, and cardiac defects are more striking in ring chromosome 15 patients and are indications for karyotyping when found in conjunction with the Russell-Silver phenotype.

A boy with ring chromosome 15 derived from a t(15q;15q) Robertsonian translocation in the mother: cytogenetic and biochemical findings

We describe a boy with a ring chromosome 15, showing the manifestations characteristic of this condition, ie, growth deficiency and unusual facial appearance with minor anomalies. The ring was derived from a t(15q;15q) chromosome of the mother, who had also had four spontaneous abortions. The respective karyotypes were 45,XX, -15,-15,+t(15q;15q) (mother) and 46,XY,-15,+r(15q;15q)mat (15q13 leads to cen leads to 15q26)(son). The ring chromosome lacked the short arms of the two translocated chromosomes 15 and was duplicated for a portion of the long arms near the centromere, probably cen leads to q13. Data from enzyme assays suggest that this duplicated region carries the alpha-mannosidase gene.

Ring (15) chromosome

Cytogenetic studies on lymphocytes from a girl aged 3 years and 10 months revealed revealed a ring chromosome 15. Several banding methods showed the r(15) chromosome not to have any apparent deletion of the long arm. The silver staining technique for nucleolar organizer regions showed an NOR positive region (band p12). In only a few cells was a chromosome 15 missing. The size of the r(15) was found to be constant. Comparison with 11 previous reported cases in the literature shows that the clinical manifestations in the different patients with ring chromosome 15 are constant although not clinically identifiable and it appears likely to attribute them to a significantly retarded intrauterine and postnatal growth instead of presumed deficiency in the long arm and mosaic configurations.

Ring chromosome 15 in a male adult with radial defects. Evaluation of the phenotype

A case of a 37-year-old male patient with r(15) is reported. At birth he was small and light for dates. His main features are: short stature, head circumference in the lower normal range, mid-facial hypoplasia, radial defects, and mental retardation. Evaluation of the phenotype led us to conclude that a wide spectrum of malformations is possible. There is apparently no strong correlation between karyotype and phenotype.

Ring chromosome 15 syndrome

Two new cases of ring chromosome 15 are reported. A review of the nine cases described in the literature shows that ring chromosomes 15 are associated with a rather uniform phenotype characterized by slight to moderate mental retardation, marked pre- and postnatal growth failure, triangular face, and short hands and feet.

Analysis of banding patterns and mosaic configurations in a case of ring chromosome 15

Cytogenetic studies on lymphocytes from a 14-year-old mentally retarded girl with somatic anomalies suggestive of a chromosomal abnormality revealed a ring chromosome 15. The long arm of the defective chromosome is broken at band q24 or q25. The silver staining technique for nucleolus organizer regions showed that the ring had lost the achromatic stalk and the satellite. The chromosomal mosaicism resulting from the structural instability of the ring chromosome was analyzed and compared with 6 cases reported in the literature. It is proposed that the clinical manifestations in the different patients with ring chromosome 15 result from both the deficiency in the long arm and the mosaic configurations.

Ring chromosome 15 in child with a minor dysmorphism of phenotype

The analysis of a karyotype of a girl with slight mental retardation, without significant dysmorphism, showed the presence of a ring chromosome in group 13-15. By the application of G technique it was discovered that in this case it was an aberrant chromosome 15. Besides retardation in growth and a slight mental backwardness in this case, it was confirmed that in cases of ring 15 syndrome no preponderant change appears in phenotype.