Abstract
Ring chromosome abnormalities are rare in comparison with other cytogenetic anomalies. They have been described in all groups except group F, mainly in the D group and in the X chromosome. It has been proposed that patients with ring chromosome aberrations involving the same chromosome should have similar phenotypes, and attempts have been made to establish the existence of definite ring syndromes.
We have studied a nine-year-old female patient who presented with coarse facial features, microcephaly, mental retardation, hirsuitism, and tapering fingers. Quinacrine-banded karyotypes derived from peripheral blood lymphocytes revealed a 46, XX, r(9) (p24→q34) pattern. Many of the facial and somatic features of our patients are distinctly different from those of other reported patients with ring-9, of which only five cases have been described. There is also little similarity to cases of 9p-, and we are unable to find reports of cases of 9q-.
These studies support the theory, suggested by others, of variable phenotypic expression of ring chromosomes. In patients with ring chromosomes showing deletions at similar regions, phenotypic variability is the probable result of a combination of factors, including moaaicism (due to the tendency of ring chromosomes to missegregate during mitosis), variable ring structure (simple and polycentric rings, presumably containing duplications and deficiencies), and resulting instability of the ring chromosome.
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Thuluvancheri, M. RING CHROMOSOME NINE: VARIABLE PHENOTYPIC EXPRESSION. Pediatr Res 11, 524 (1977). https://doi.org/10.1203/00006450-197704000-00925
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DOI: https://doi.org/10.1203/00006450-197704000-00925