Detection of submicroscopic aberrations in patients with unexplained mental retardation by fluorescence in situ hybridization using multiple subtelomeric probes

PURPOSE

To further assess the frequency of subtelomeric aberrations in a selected population and to examine the feasibility of a clinical testing.

METHODS

Patients were selected based on the following criteria: (1) mental retardation (IQ < 70) or developmental delay with dysmorphic features; (2) a normal karyotype at the level of resolution of 450 to 500 bands; and (3) exclusion of other possible etiologies by a full genetic assessment and relevant tests. Fluorescence in situ hybridization (FISH) was performed using multiple subtelomeric probes. Abnormal findings were confirmed by 24-color spectral karyotyping or FISH with a specific subtelomeric probe, and family studies were carried out to determine inheritance.

RESULTS

Clinically significant aberrations were detected in 6 of 150 proband patients (4%), while deletion of the 2q subtelomeric region appeared to be a common variant (6%).

CONCLUSIONS

FISH with multiple subtelomeric probes is a valuable clinical test for establishing a definitive diagnosis for patients with unexplained mental retardation/developmental disorders.

Midtrimester genetic amniocentesis in eastern Ontario: a review from 1970 to 1985

Greater use of genetic amniocentesis in the Eastern Ontario region occurred once the results from the various national trials were published. Acceptance also paralleled an increase in the number of low parity older women having children and the centralisation and greater publicity given to our programme in the late 1970s. A centralised approach has had the positive effects of preventing unnecessary procedures, assuring appropriate patient counselling, follow up, and review, and of increasing obstetric and laboratory expertise. Advanced maternal age has been largely responsible for the increased demand for the service and accounted for an increasing proportion of tests performed, while the absolute number for several other diagnostic categories remained unchanged. We found no evidence that women with a history of previous miscarriage had a higher rate of pregnancy loss following the procedure, and comparison with a group of women who declined amniocentesis did not show that the test increased the risk of miscarriage.

Detection at amniocentesis of a maternally inherited X;Y translocation

G banded chromosomal analysis of cells from a routine amniocentesis revealed a Y to X translocation in the fetus. The same unbalanced translocation was found in the mother who was disproportionately short. H-Y antigen titers in the mother were intermediate and steroid sulfatase activity was in the normal female range. At birth the baby exhibited few dysmorphic features but appeared to have short limbs.