A patient with Prader-Willi syndrome and a supernumerary marker chromosome r(15)(q11.1-13p11.1)pat and maternal heterodisomy

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.

Infantile spasms in a mosaic monocentric and duplicated SMC 15 patient

OBJECTIVE

To report detail of a patient with infantile spasms whose cytogenetic analysis revealed mosaic monocentric and duplicated supernumerary marker chromosome (SMC) 15.

SUBJECT AND METHODS

The subject for this case was a 13-month-old girl with infantile spasms and delayed developmental milestones. Chromosomal analysis with G-band showed the presence of SMC in mosaic. Further investigations using in situ hybridization, methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA), microsatellite marker, and single nucleotide polymorphism (SNP) array analysis were performed.

RESULTS

Her karyotype was noted as mosaic 47,XX,+mar[26]/46,XX[4], ish der(15)(D15Z1+, SNRPN++, PML-) de novo. MS-MLPA analysis showed that the Prader-Willi syndrome/Angelman syndrome critical region is highly methylated, and microsatellite marker analysis proved that the 15q11.2 region of the patient comprises three kinds of alleles: one paternal and two maternal. SNP array analysis suggested an asymmetric structure of SMC(15) composed of 15q11-q13 recombination at breakpoint (BP) 4:BP5.

CONCLUSIONS

This is the first report of SMC(15) with monocentric and duplicated proximal 15q. The clinical presentations are quite similar to those of isodicentric chromosome 15 syndrome. The results of microsatellite and SNP array analysis suggest two possibilities regarding the timing of the mosaic SMC(15) formation. One possibility is that it occurred during maternal meiosis, and the other possibility is formation during a very early stage of embryo development that was initially trisomic of chromosome 15.

Ophthalmic treatment and vision care of a patient with rare ring chromosome 15: a case report

The Aim. Ring chromosome 15 is a very rare genetic abnormality with a wide spectrum of clinical findings. Up to date, about 50 cases have been documented, whereas no reports on ophthalmological treatment of such patients have been published. The aim of this study is not only to describe a new patient, but also, for the first time, to present the results of nonoperative management of divergent strabismus. Material and Methods. We present an amblyopic patient with 46,XX, r(15) karyotype: treated conservatively for exotropia of 60 prism diopters. The management consisted of refractive and prismatic correction, eye occlusion, and orthoptic exercises between the age of 15 months and 8 years. Results. The deviation angle of exotropia was decreased to 10 prism diopters, the visual acuity improved to 1.0 in both eyes (Snellen chart) and the fixation pattern was normal. The prisms enabled permanent symmetrical stimulation of the retina, which lead to a development of normal single binocular vision (Maddox test, filter test, and synoptophore tests). Conclusions. Parental karyotype was normal; the analysis of a three-generation pedigree has shown no genetic abnormalities or pregnancy losses so the child's karyotype anomaly was classified as de novo that is a single occurrence of this type of chromosomal disorder in this family. Strabismus in ring chromosome 15 patients is a difficult condition to manage, although success may be achieved.

Primary testicular dysfunction is a major contributor to abnormal pubertal development in males with Prader-Willi syndrome

BACKGROUND

Recent studies challenge the assumption that hypogonadism in Prader-Willi syndrome (PWS) is due only to hypothalamic dysfunction.

OBJECTIVES

The aims of the study were to characterize sexual development and reproductive hormones in PWS males and investigate the etiology of hypogonadism.

METHODS

Physical examination and blood sampling were performed on 37 PWS males, ages 4 months to 32 yr.

RESULTS

All had a history of undescended testes; age at orchiopexy ranged from 2 months to 6 yr. Pubertal signs were variable, but none achieved full genital development. Anti-Mullerian hormone (AMH) levels in PWS boys were near the lower limits of normal, decreasing from 44.4 +/- 17.8 ng/ml (mean +/- sd) in young children to 5.9 +/- 4.7 ng/ml in adolescents, similar to normal males. In contrast, inhibin B was consistently low (27.1 +/- 36.1 pg/ml) or undetectable in all age groups. In adult males, FSH levels were high (20.3 +/- 18.3 IU/liter), LH levels were normal (4.2 +/- 4.3 IU/liter), and testosterone levels were low (1.87 +/- 1.17 ng/ml). Only two adults had severe hypogonadotropic hypogonadism with undetectable levels of LH and FSH and high AMH levels (34.9 and 36.7 ng/ml), unlike the other nine adults with AMH levels 2.6 +/- 2.1 ng/ml. Androstenedione (1.06 +/- 0.30 ng/ml) and DHEAS (281.1 +/- 143.6 microg/dl) in adult PWS were normal.

CONCLUSIONS

Pubertal development in PWS is characterized by normal adrenarche, variable hypothalamic dysfunction, and hypogonadism due to a unique testicular defect. Primary testicular dysfunction is a major component of hypogonadism in PWS.

Characterization of an autism-associated segmental maternal heterodisomy of the chromosome 15q11-13 region

Cytogenetic abnormalities in the Prader-Willi/Angelman syndrome (PWS/AS) critical region have been described in individuals with autism. Maternal duplications and linkage disequilibrium in families with autism suggest the existence of a susceptibility locus at 15q11-q13. Here, we describe a 6-year-old girl diagnosed with autism, developmental delay, and delayed expressive and receptive language. The karyotype was designated de novo 47, XX, idic(15)(q13). Fluorescence in situ hybridization (FISH) and molecular analysis with 15q11-q13 markers revealed an additional copy of the region being of maternal origin. Duplication of the 15q11-q13 segment represents the most consistent known chromosomal abnormality reported in association with autism. This present case report reinforces the hypothesis that additional copies of this chromosome segment are causally related to autism.

A case of mosaic supernumerary ring chromosome 15 with two copies of the segment 15p11.1-q14

Although supernumerary marker chromosomes derived from chromosome 15 (SMC(15)) are the most common marker chromosome in humans, ring SMC(15)s are rare. Here we report on a 16-month-old patient who has a ring SMC(15) with two copies of the segment 15p11.1-q14 region. She exhibits hypotonia, developmental delay, speech delay, microstomia, micrognathia, and other mild dysmorphic features. The ring was present in 22% of her peripheral blood lymphocyte cells. FISH study revealed that the ring was derived from chromosome 15, and had neither telomere sequence nor satellite III paracentromeric DNA. It had alpha satellite DNA, and two copies of the segment 15q11.2 to CTD 2125J1 (at 15q14, 2.2 Mbp telomeric of the common breakpoint 5). The ring-containing cells had four copies of 15p11.1-q14. The ring can be described as r(15)(::p11.1 --> q14::q14 --> p11.1::). Southern-blot analysis of the methylation pattern in the PW/AS critical region showed biparental inheritance, and the ring was maternally derived. This patient's phenotype was comparable to ring SMC(15) patients with three copies of the Prader-Willi/Angelman syndrome (PWS/AS) critical region.