Table1. Inherited familial balanced complex chromosomal rearrangements, involving four chromosomes

Adj 1 - adjacent type 1; Alt - alternative

In most pedigrees with segregation of a complex rearrangement through several generations described so far, not only the transmission of the complete balanced rearrangement but also inheritance of only part of the rearrangement, in balanced and unbalanced forms, have been observed [5,6,11]. To our knowledge only Meer et al 1981 [12] have not found any unbalanced karyotypes within a large pedigree. They reported only balanced and normal karyotypes among live births.
A small number of BCT are detected during prenatal diagnosis. To our knowledge the reported case is the second with familial 4-way balanced chromosome translocation identified during prenatal diagnosis. BCT observed in cultured amniocytes are a serious problem in genetic counseling and it is difficult to predict the outcome of pregnancy and the chances for normal development especially in the de novo cases [Table 2].

Table 2 Balanced complex translocations involving four chromosomes identified during prenatal diagnosis.

Ih- inherited, dn - de novo, nt - not tested, F- female, M - male.

In the reported family the revealed balanced complex translocation is associated with reproductive problems. Spontaneous abortions in the family have not been studied cytogenetically and it is not known if they carried unbalanced chromosome complements. Some of the families reported in the literature had only spontaneous abortions and others - only abnormal children.
Various types of segregation of the t(1;4;20;9) will result in different karyotype configurations. Since the observed translocation is a 4-way with one breakpoint on each involved chromosome it is in some instances similar to balanced reciprocal translocations involving 2 chromosomes that form quadrivalent during meiosis. The formation of a octavalent during gametogenesis gives the possibility of formation of severely unbalanced gametes. The alternate type of segregation, without cross-over in the interstitial segments will result in all gametes having the balanced rearranged or the normal chromosome complement. Any adjacent (-1 or -2) without cross-over or the alternate type with cross-over in one interstitial segment will result in all gametes being unbalanced, having both a duplication and a deficiency. Recombinations are not expected.

Fig4. Pedigree of the reported family. The carriers of the balanced translocation are indicated by arrows

Because the new born child is male, his growth will be followed up after birth and we will particularly pay attention to his puberty, because as Rodriquez et al 1985 [9], Chandley et al 1975[7], Josef et al 1982[8] cited male carriers of complex chromosomal rearrangements involving four chromosomes have an increased risk of being infertile.