Clinical and cytogenetic aspects of the 21 deletion syndrome.

The clinical, cytogenetic and dermatoglyphic findings in a patient with a ring chromosome 21 are presented. This anomaly acts as a deletion of chromosomal material and results in specific congenital defects. A comparison is made with 24 cases of deletions involving chromosome 21 described in the literature. Six of these have been studied by means of recently developed chromosome banding techniques. Cases presumably arise through somatic non-disjunction or chromosome breakage. When the chromosomes of both parents are normal the recurrence risk is negligible.