Abstract
The two year old proband has multiple malformations and severe developmental delay. Her karyotype is 46, XY, -9, +rec(9), dup p, inv(9)(q22.1q34.3)mat, with a net duplication of 9pter←q22.1 and deficiency of distal 9q34.3←qter. The rec(9) was derived by two crossovers, one within the inversion loop. The mother's karyotype is 46, XX, inv(9)(q22.1q34.3). Her chromosomes 9 differ in that the #9 with tie inversion has some heterochromatin in the short arm as a normal variant. In the proband's rec(9), the variant centromere is now attached to the normal 9q, which indicates that during maternal meiosis there was a crossover between 9ql2 and 9q22. The rec(9) was present and stable in over 300 lymphocyte metaphase cells. Most rec(9)'s had one primary constriction at the centromere within the normal 9q segment. This centromere was Cd-positive, and the second centromere was Cd-negative, but 18% of routine Giemsa-stainad cells had two primary constrictions. In the proband's fibroblast cells harvested in situ without colcemid, nuclear projections were observed in 10% of interphase cells. Such nuclear projections have been observed whenever a chromosome with one active centromere and one latent centromere is present, suggesting that there was at least some spindle-fiber activity of the latent centrcraere (Am J Hum Genet 26:83, 1974 & Proc Clin Boil Res 26:181, 1978). In situ hybridization with a centromere specific probe (p82H) and a paracentromere specific probe (L6) revealed no differences between the two C-band regions of the rec(9). This suggests that there was no interstitial deletion of heterochromatic or centromeric material. The present case confirms that a stable recombinant chromosome derived fron a paracentric inversion can lead to malformations and suggests that prenatal diagnosis should be made available to families with paracentric inversions.
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Worsham, M., Miller, D., Bebu, V. et al. A RECOMBINANT CHROMOSOME 9 DERIVED FROM A MATERNAL PARACENTRIC INVERSION: CYTOGENETICS, INTERPHASE NUCLEAR PROJECTIONS, AND IN SITU HYBRIDIZATION USING CENTROMERE AND PARACENUOMERE. Pediatr Res 21 (Suppl 4), 295 (1987). https://doi.org/10.1203/00006450-198704010-00770
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DOI: https://doi.org/10.1203/00006450-198704010-00770