Complex chromosome rearrangements involving chromosomes 1;3 and 2;3 in two abnormal children

Structural chromosomal anomaly in mental retardation

This article reports the structural chromosomal anomaly in three patients with mental retardation: (i) Proband was a five year old girl with reciprocal retardation (1; 2) (p32; q11) (ii) Proband, female of 14 years. Her karyotype showed translocation (1; 3) (q42; q13). The translocations were de novo in origin (iii) Proband showed variant 13 as the giant satellite over its short arm, and this was paternal in origin. Proband, eighteen months old male child had microcephaly and seizures. These two features may be because of autosomal recessive condition. This report emphasises the need for kayotyping to provide a clear cut diagnosis and appropriate counselling.

Complex chromosome rearrangement involving chromosomes 1, 4 and 16 revealed by fluorescence in situ hybridization

A 7-year-old boy with mental retardation had apparently balanced reciprocal translocations, involving the telomeric regions of chromosomes 1p and 4q, which was detected by routine chromosome analysis. Fluorescence in situ hybridization (FISH) was used and also revealed the telomeric region of chromosome 16p to be involved in a still apparently balanced translocation-complex, impossible to discover with classical cytogenetic analysis. We want to emphasize the importance of FISH in detecting small chromosomal aberrations. We discuss whether the abnormal phenotype is caused by unbalanced karyotype with cryptic undetected translocations or small deletions or mutations in the translocation-breakpoints.

Prenatally diagnosed de novo apparently balanced complex chromosome rearrangements: two new cases and review of the literature

Complex chromosome rearrangements (CCR) are rare structural rearrangements. Currently six cases of prenatally diagnosed balanced de novo CCR have been described. We present two new cases of prenatally ascertained balanced de novo CCR. In the first case, an amniocentesis revealed a balanced de novo three-way CCR involving chromosomes 5, 6, and 11 with a pericentric inversion of chromosome 5 [four breaks]. In the second case, a balanced de novo rearrangement was identified by amniocentesis which involved a reciprocal translocation between chromosomes 3 and 8 and a CCR involving chromosomes 6, 7, and 18 [six breaks]. The use of whole chromosome painting helped elucidate the nature of these rearrangements. A review of the postnatally ascertained cases suggests that most patients have congenital anomalies, minor anomalies, and/or developmental delay/mental retardation. In addition, there appears to be a relationship between the number of chromosome breaks and the extent of phenotypic effects. The paucity of information regarding prenatally diagnosed CCR and the bias of ascertainment of postnatal CCR cases poses a problem in counseling families.

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.