Trisomy 3q25.1-qter and monosomy 8p23.1-pter in a patient: cytogenetic and molecular analysis with delineation of the phenotype

Homozygous microdeletion of the ERI1 and MFHAS1 genes in a patient with intellectual disability, limb abnormalities, and cardiac malformation

A male child, born from consanguineous parents and having intellectual disability, short stature, dysmorphic facial features, synpolydactyly, and cardiac malformations is reported. Chromosomal microarray analysis showed that the patient presents with an 8p23.1 homozygous deletion, containing the microRNA miR-4660, the exoribonuclease 1 (ERI1), and malignant fibrous histiocytoma amplified sequence 1 (MFHAS1) genes. The microRNA miR-4660 has no known function. MFHAS1 is an immunomodulatory protein involved in Toll-like receptor signaling, erythropoiesis, and cancer. ERI1 is a ribonuclease involved in RNA metabolism and is required for the correct patterning of the skeleton by defining the HOXC8 expression. We discuss the involvement of these deleted genes to the patient's features and highlight differential diagnoses with syndromes implicating limb extremity abnormalities such as synpolydactyly, including the monosomy 8p.

Retrospective karyotype study in mentally retarded patients

OBJECTIVE

To describe the chromosomal alterations in patients with mental retardation (MR) using G-banding karyotype analysis.

METHOD

A retrospective study of the results G-banding karyotype analysis of 369 patients investigated for MR was performed. Based on the structural rearrangements found, the authors searched all chromosomal regions related with breakpoints, and these were compared with the literature on MR and databases.

RESULTS

338 (91.6%) normal cases, and 31 (8.4%) with some type of chromosomal abnormality were identified. Among the altered cases, 21 patients (67.8%) were identified with structural chromosomal alterations, nine (29%) with numerical alterations, and one (3.2%) with numerical and structural alterations.

CONCLUSION

Structural chromosomal abnormalities were observed more frequently in this study. G-banding karyotyping contributes to the investigation of the causes of MR, showing that this technique can be useful for initial screening of patients. However, higher resolution techniques such as array based comparative genomic hybridization (aCGH) and multiplex ligation-dependent probe amplification (MPLA) can detect submicroscopic alterations commonly associated with MR.

Secondary complex chromosome rearrangement identified by chromosome analysis and FISH subsequent to detection of an unbalanced derivative chromosome 12 by SNP array analysis

Microarray analysis is used to detect small copy number changes (deletions and duplications) that may be associated with genetic syndromes and phenotypic abnormalities. However, there are limitations to what microarrays are able to detect. We present a patient referred for microarray in whom chromosome analysis identified a more complex structural rearrangement than was indicated by the microarray. Our studies included Affymetrix Cytoscan HD array, chromosome analysis and fluorescence in situ hybridization (FISH) using a subtelomere probe targeting chromosome 3. Array analysis revealed a 6.45-Mb terminal duplication of 3q28q29 and a 1.02-Mb terminal deletion of 12p13.33. This suggested an unbalanced translocation derivative. In order to investigate visibility of the rearrangement, chromosome analysis was performed, revealing an additional balanced complex chromosome rearrangement involving chromosomes 3 and 11, including a translocation with breakpoints at 3p13 and 11p11.2, as well as a paracentric inversion of segment 3p25p13 translocated onto chromosome 11. Subtelomere FISH confirmed that the duplicated chromosome 3q material observed in the array analysis was localized to distal 12p. This case clearly illustrates the combined utilization of classic cytogenetics, FISH and array technologies to better characterize chromosomal abnormalities.

8p deletion and 9p duplication in two children with electrical status epilepticus in sleep syndrome

We describe two individuals with the same chromosomal aberrations derived from an unbalanced translocation between chromosomes 8p and 9p, who presented with intellectual disabilities, dysmorphic features, and localization-related epilepsy. Several years after the onset of epilepsy, aggravation of widespread epileptic discharges during sleep resulted in the emergence of absence and/or atonic seizures in both patients; one patient additionally presented with psychomotor deterioration. These symptoms completely disappeared after treatment with ethosuximide and benzodiazepines, and marked improvement was observed in electroencephalographic findings. We review the clinical features of der(8)t(8;9) with particular focus on epileptic complications. We conclude that particular types of chromosomal aberrations may have a propensity to develop the condition categorized as electrical status epilepticus in sleep.

Prenatally diagnosed partial trisomy 3q case with an omphalocele and less severe phenotype

Trisomy 3q is a very rarely reported chromosomal disorder. Duplication of part of the long arm of human chromosome 3 causes a distinct and severe syndrome that leads to multiple congenital abnormalities. A 27 year-old pregnant woman was admitted to our clinic at 17 weeks of gestation. Prenatal sonography identified a fetus with an omphalocele that contained the liver and bowel, mild ventriculomegaly and polyhydramnios. Amniocentesis revealed the karyotype of 46, XY, der (3) (3qter→3q21: : 3pter→3qter). The pregnancy was subsequently terminated. Postnatally, the proband showed midfacial hypoplasia, micrognathia, hypoplastic 12th ribs, omphalocele and prominent heels. We reported this partial trisomy 3q case because he had less marked malformations compared to other reported cases and also different features such as an omphalocele and hypoplastic 12th rib which have not been described previously in an isolated Trisomy 3q case with this karyotype.

Phenotype in X chromosome rearrangements: pitfalls of X inactivation study

OBJECTIVE

X inactivation pattern in X chromosome rearrangements usually favor the less unbalanced cells. It is correlated to a normal phenotype, small size or infertility. We studied the correlation between phenotype and X inactivation ratio in patients with X structural anomalies.

PATIENTS AND METHODS

During the 1999-2005 period, 12 X chromosome rearrangements, including three prenatal cases, were diagnosed in the Laboratoire de Cytogénétique of Strasbourg. In seven cases, X inactivation ratio could be assessed by late replication or methylation assay.

RESULTS

In three of seven cases (del Xp, dup Xp, t(X;A)), X inactivation ratio and phenotype were consistent. The four other cases showed discrepancies between phenotype and X inactivation pattern: mental retardation and dysmorphism in a case of balanced X-autosome translocation, schizophrenia and autism in two cases of XX maleness and MLS syndrome (microphthalmia with linear skin defects) in a case of Xp(21.3-pter) deletion.

CONCLUSION

Discrepancies between X inactivation ratio and phenotype are not rare and can be due to gene disruption, position effect, complex microrearrangements, variable pattern of X inactivation in different tissues or fortuitous association. In this context, the prognostic value of X inactivation study in prenatal diagnosis will be discussed.