Ring chromosome 10 (p15q26) in a patient with unipolar affective disorder, multiple minor anomalies, and mental retardation

Expanding the Neurological Phenotype of Ring Chromosome 10 Syndrome: A Case Report and Review of the Literature

Ring chromosome 10 [r(10)] syndrome is a rare genetic condition, currently described in the medical literature in a small number of case report studies. Typical clinical features include microcephaly, short stature, facial dysmorphisms, ophthalmologic abnormalities and genitourinary malformations. We report a novel case of r(10) syndrome and review the neurological and neuroradiological phenotypes of the previously described cases. Our patient, a 3 year old Italian girl, represents the 20th case of r(10) syndrome described to date. Intellectual disability/developmental delay (ID/DD), microcephaly, strabismus, hypotonia, stereotyped/aggressive behaviors and electroencephalographic abnormalities were identified in our patient, and in a series of previous cases. A brain MRI disclosed a complex malformation involving both the vermis and cerebellar hemispheres; in the literature, posterior cranial fossa abnormalities were documented by CT scan in another case. Two genes deleted in our case (ZMYND11 in 10p and EBF3 in 10q) are involved in autosomal dominant neurodevelopmental disorders, characterized by different expressions of brain and posterior cranial fossa abnormalities, ID/DD, hypotonia and behavioral problems. Our case expands the neurological and neuroradiological phenotype of r(10) syndrome. Although r(10) syndrome represents an extremely rare condition, with a clinical characterization limited to case reports, the recurrence of specific neurological and neuroradiological features suggests the need for specific genotype-phenotype studies.

Clinical, cytogenetic and molecular study of a case of ring chromosome 10

Ring chromosome 10 is a rare cytogenetic finding. Only a few cases with molecular cytogenetic definition have been reported. We report here on a child with a ring chromosome 10, which is associated with prenatal and postnatal growth retardation, microcephaly, dysmorphic features, hypotonia, heart defect, severe pes equinovarus, and bronchial asthma. The chromosomal aberration was defined by chromosome microarray analysis, which revealed two deletions at 10pter (3.68 Mb) and 10qter (4.26 Mb). The clinical features are very similar to those reported in other clinical cases with ring chromosome 10, excluding bronchial asthma, which has not been previously reported in individuals with ring chromosome 10.

Ring chromosome 10: report on two patients and review of the literature

Ring chromosome 10--r(10)--is a rare disorder, with 14 cases reported in the literature, but only two with breakpoint determination by high-resolution techniques. We report here on two patients presenting a ring chromosome 10, studied by G-banding, fluorescent in situ hybridization (FISH), multiplex ligation-dependent probe amplification (MLPA) and SNP-array techniques, in order to investigate ring instability and determine breakpoints. Patient 1 showed a r(10)(p15.3q26.2) with a 7.9 Mb deletion in 10q26.2-q26.2, while patient 2 showed a r(10)(p15.3q26.13) with a 1.0 Mb deletion in 10p15.3 and a 8.8 Mb deletion in 10q26.13-q26.3, both unstable. While patient 1 presented with clinical features usually found in patients with r(10) and terminal 10q deletion, patient 2 presented characteristics so far not described in other patients with r(10), such as Dandy-Walker variant, osteopenia, semi-flexed legs, and dermal pigmentation regions. Our data and the data from literature show that there are no specific clinical findings to define a r(10) syndrome.

Chromosome r(10)(p15.3q26.12) in a newborn child: case report

Background

Ring chromosome 10 is a rare cytogenetic finding. Of the less than 10 reported cases we have found in the literature, none was characterized using high-resolution microarray analysis. Ring chromosomes are frequently unstable due to sister chromatid exchanges and mitotic failures. When mosaicism is present, the interpretation of genotype-phenotype correlations becomes extremely difficult.

Results

We report on a newborn girl with growth retardation, microcephaly, congenital heart defects, dysmorphic features and psychomotor retardation. Karyotyping revealed a non-mosaic apparently stable ring chromosome 10 replacing one of the normal homologues in all analyzed metaphases. High-resolution oligonucleotide microarray analysis showed a de novo approximately 12.5 Mb terminal deletion 10q26.12 -> qter and a corresponding 285 kb terminal deletion of 10pter -> p15.3.

Conclusion

This case demonstrates that an increased nuchal translucency thickness detected by early ultrasonography should preferably lead to not only QF-PCR for the diagnosis of Down syndrome but also karyotyping. In the future, microarray analysis, which needs further evaluation, might become the method of choice. The clinical phenotype of our patient was in agreement with that of patients with a terminal 10q deletion. For the purpose of genotype-phenotype analysis, there seems to be no need for a "ring syndrome" concept.

A subterminal deletion of the long arm of chromosome 10: a clinical report and review

We report on a girl with mental retardation, dysmorphic features, and behavioral problems. A small terminal deletion of the long arm of chromosome 10 was detected by subtelomeric fluorescence in situ hybridization (FISH) studies in all analyzed metaphases. The deletion was shown to be a de novo terminal deletion of approximately 6.1 Mb, with the deletion breakpoint localized at band 10q26.2, between BAC probes RP11-498K22 and RP11-42K2. A subterminal 10q deletion as found in the present patient has, to our knowledge, only been reported in 15 patients (including 8 familial cases). We review the clinical and behavioral phenotype of these patients with "pure" subterminal 10q deletion.

Mosaic ring 20 with no detectable deletion by FISH analysis: Characteristic seizure disorder and literature review

Ring chromosome 20 is a rare chromosome disorder characterized by a typical seizure phenotype consisting of complex partial seizures, frequent progression to generalized tonic or tonic-clonic seizures, and nocturnal frontal lobe seizures with frequent episodes of non-convulsive status epilepticus. Development may be normal or mildly delayed, followed by cognitive and behavioral decline after seizure onset. Here, we describe a patient with a typical severe seizure phenotype and a mosaic ring chromosome 20 without loss of p or q subtelomere regions or telomeric sequences. The ring had a longer telomere length than either of the telomere ends of its homologous chromosome 20 by quantitative fluorescence in situ hybridization analysis, suggesting that it might be derived from telomere-telomere fusion. The phenotypic comparison of this patient and other chromosome 20 cases that had terminal deletions of 20qter (n = 1) and 20pter (n = 7), shows that the epilepsy phenotype and electroencephalographic abnormalities are characteristic in patients with ring chromosome 20. Several hypotheses have been proposed to address the elusive mechanisms underlying the seizure disorder in ring chromosome 20. These possibilities include haploinsufficiency of two epilepsy genes CHRNA4 and KCNQ2 located at 20qter, silencing of these genes by a telomere position effect, or microdeletions or rearrangements of genetic material during the ring formation.