Complex chromosomal rearrangement leading to partial trisomy 22

Complex chromosome rearrangement with ankyloblepharon filiforme adnatum

A Caucasian boy with a de novo complex chromosome rearrangement owing to six chromosome breaks was small for gestation with microcephaly, complex heart defect, hypotonia, left auricular pit, simian creases, and ankyloblepharon filiforme adnatum. The rearrangement included two translocation, t(15;21) (q22;q22) and t(3;11)(q21;q11), with the derivative 3 showing in addition pericentric inversion (p11q11) and interstitial deletion (q11q21). Based on parental satellite polymorphisms of chromosomes 15 and 21, the paternal gamete appeared to be the source of the chromosome rearrangement. There was no evidence of mitotic chromosome instability. A review of 36 reported patients with complex chromosome rearrangements secondary to more than four breaks indicates that complex chromosome rearrangements are compatible with gamete survival, zygote formation, and postnatal life. The latter is usually compromised by structural defects, growth retardation, and often mental retardation.

Cleft palate and complex chromosome rearrangements

Two of three unrelated children with de novo congenital complex chromosome rearrangements (CCR) with more than four chromosome breaks had cleft lip and palate as one of several congenital anomalies. In patient 1, unilateral complete cleft of the primary and secondary palates accompanied severe ectrodactyly, bilateral posterior choanal atresia and several minor congenital anomalies. Karyotypes of peripheral lymphocytes and skin fibroblasts showed five derivative chromosomes with six break points. There were two translocations, t(2;5), t(3;11) and an interstitial deletion, del(13)(q12q14). Patient 2 had a bilateral complete cleft of the lip and palate, in addition to slow pre- and postnatal growth and minor congenital anomalies. Peripheral lymphocytes and palatal mucosa fibroblasts karyotypes showed five derivative chromosomes with six break points. A partial deletion of 10p, two translocations, t(2;3), t(7;18) and an inversion of the derivative chromosome 2 were present. In both patients, a "major catastrophe" of unknown etiology in one of the parental gametes appeared to be the event leading to the stable CCR without evidence of persistent chromosome instability. All four parents had normal karyotypes. The presence of palatal clefts in these patients indicates that dysmorphologists and pediatricians have to consider CCR whenever taking care of a patient with cleft palate, particularly if additional anomalies, no matter how subtle, are present. The detection and interpretation of the latter anomalies are essential for the diagnosis and management of these patients. Accurate cytogenetic diagnosis determines the short- and long-term prognosis and facilitates genetic counseling in regard to life-span, quality of life and reproductive plans of patients and parents.

Complex chromosome rearrangements and congenital anomalies

Congenital complex chromosome rearrangements (CCR) compatible with life are rare in man. Thus patients with CCR usually present considerable diagnostic difficulties both clinically and cytogenetically. We studied a 12-year-old mentally retarded male with minor congenital anomalies as described below and his first-degree relatives. The propositus had an unbalanced karyotype with eight break points and seven derivative chromosomes; two deletions, del(6) (q25----qter) and del(14) (q31----qter), and four translocations, t(2;11), t(5;15), t(6;11), t(6;20) were present. Parental chromosomes were normal; however, the mother had a few metaphases with abnormal chromosomes suggestive of chromosome instability. These findings and a review of reported patients with CCR are presented with regard to speculations about etiology, pathogenesis, phenotypic expression, and prognosis. Physicians should be aware of CCR and broader indications for cytogenetic studies appear warranted in view of these data.