PARACENTRIC INVERSIONS IN HUMANS - A REVIEW OF 446 PARACENTRIC INVERSIONS WITH PRESENTATION OF 120 NEW CASES

We present a large review of 446 cases of paracentric inversions (PAI) , including 120 new cases, to assess their incidence, distribution, in heritance, modes of ascertainment, interchromosomal effects, viable re combinant offspring, and clinical relevance. All 23 autosomes and sex chromosomes had inversions. However, none were identified in chromosom e arms 18p, 19q, 20q, and Yp. PAT were most commonly reported in chrom osomes 1, 3, 5, 6, 7, 11, and 14 and less frequently in chromosomes 4, 16, 17, 18, 19, 20, 21, 22, and Y. Inversions were most common in chr omosome arms 6p, 7q, 11q, and 14q and observed least in chromosome arm s 2p, 2q, 3q, 4q, and 6q. Frequently encountered breakpoints included 3(p13p25), 6(p12p23), 6(p12p25), 7(q11q22), and 11(q21q23). Ascertainm ent was primarily incidental (54.5%), mental retardation and/or congen ital anomalies (22.2%), spontaneous abortions (11.4%), associations wi th syndromes (3.0%), and infertility (2.0%) accounted for the remainde r. Ascertainment was neither related to the length of the inverted seg ment nor to specific inversions except for PAI of Xq which often prese nted with manifestations of Ullrich-Turner syndrome. Sixty-six percent of PAI were inherited while 8.5% were de novo. Recombination was obse rved in 17 cases, 15 of which resulted in a monocentric chromosomal de letion or duplication. No common factors were identified that suggeste d a tendency towards recombination. The incidence of viable recombinan ts was estimated to be 3.8%. This review documents that PAI are perhap s more commonly identified than suggested in previous reviews. Despite the possible bias of ascertainment in some cases, there may be associ ated risks with PAI that require further examination. Our data suggest that PAI carriers do not appear to be free of risks of abnormalities or abnormal progeny and caution is recommended when counseling. (C) 19 95 Wiley-Liss, Inc.