Angelman's syndrome and 15q11-13 deletions.

In the February issue of the journal we read with interest the paper by Pembrey et al.1 After their initial finding of this type of deletion in two patients they were able to re-examine 10 patients who have "a secure diagnosis of Angelman's syndrome". In four of these an interstitial del(15) (qllql3) was found. In one other case a pericentric inversion inv(15)(pllql3) was found, which was also present in his normal mother. Two of the patients with an undetectable chromosomal deletion had an affected, or possibly affected, sib. During the past few months we have had the opportunity to perform high resolution G banded chromosome studies in 10 patients (nine girls and one boy) who had been diagnosed as having Angelman's syndrome in the past. Eight were isolated cases and two were sisters. In six of the 10 patients the presence of a del(15)(qllql3) was detected. As in the experience of Pembrey et al, a deletion was not seen in the two sibs with this MCA/MR syndrome. The present data confirm that with the available cytogenetic techniques a 15qll-13 deletion can be visualised in at least half of the patients with Angelman's syndrome. The data also support the conclusion of Pembrey et al that de novo visible deletions and autosomal recessive cases combined give an overall sib recurrence risk of less than 25%.