[Pericentric inversion of chromosome 2 (p11 q13) in unrelated families (author's transl)]

The significance of pericentric inversions of chromosome 2

Thirteen new cases of a pericentric inversion 2 collected from different laboratories are reported. In addition 41 cases of a pericentric inversion 2 were reviewed from the literature. The pooled data were analysed using Weinberg's proband method to evaluate the risk of a carrier for either children with congenital anomalies or reproductive wastage. In the "corrected" sample of 166 lifeborn offspring of carriers of a pericentric inversion 2 there were five who showed phenotypic anomalies and two died a few hours after delivery. The reported anomalies are heterogeneous and probably reflect the basic risk of any couple for abnormal lifeborn offspring. There has been no observation of a lifeborn who inherited an unbalanced recombination of a parental pericentric inversion 2. A carrier of a pericentric inversion 2 obviously has an increased risk for reproductive wastage. This is indicated by (1) an increase of the rate of spontaneous abortions and (2) an increase of the rate of index patients ascertained because of previous miscarriages. The risk of a carrier of a pericentric inversion 2 for a spontaneous abortion or a stillbirth may be about twice the basic risk of the general population.

Inversion of chromosome 2 (p11p13): frequency and implications for genetic counselling

Two cases of a pericentric inversion of chromosome 2 were found amongst 3619 blood specimens referred for karyotypic analysis. An additional three cases were identified within 1820 pregnancies presenting for genetic amniocentesis because of late maternal age. The implications for management in these cases are discussed.

Familial pericentric inversion (10) and its effect on two offspring

A pericentric inversion (10)(p15q24) was observed in three generations of a family. One daughter of the inversion carrier was found to have the inv(10) and trisomy 18. The other offspring had a recombinant (10) chromosome.

Two pericentric inversions, inv(2)(p11q13) and inv(5)(p13q13), in a patient referred for psychiatric problems

Two pericentric inversions were found in the karyotype of a male patient referred for psychiatric problems. Cytogenetic analysis, using conventional Giemsa staining and G and C banding techniques, revealed a pericentric inversion in chromosome 2, inv(2)(p11q13), and chromosome 5, inv(5)(p13q13) (fig 1). Subsequent family studies showed that the proband's father carried both inversions also (fig 2), while other members were found to be carriers of either the inverted 2 or the inverted 5. To our knowledge, this is the first report of two pericentric inversions to be found in the human genome.

Aspects of evaluation, significance, and evolution of human C-band heteromorphism

The C-band heteromorphism may be evaluated in different forms. The results obtained from classification are easily influenced by subjective factors, and the conclusions of such types of data are acceptable only if they are well matched with a control. The length measurement is simple to obtain, and a quantitative presentation of the data, with correction for the contraction stage of the chromosomes, is considered the most efficient method to evaluate the C-band size heteromorphism. Excluding the acrocentrics, whose short arms present a complex heteromorphism, and the chromosome Y, whose variable C band is terminal, all others present C-band location heteromorphism except pair 16. It is possible to multiply the detectable heteromorphisms in some bands by using diverse staining methods. The present state of knowledge about the role of heterochromatin in the cell is analyzed, as is the effect of C-band variability on the phenotype, the reproductive fitness, and the individual viability. Although a great amount of data is available, no result can be considered definitive as yet. Aspects in which the use of C-band heteromorphisms are profitable are considered.

Study on segregation and risk for abnormal offspring in carriers of pericentric inversion of the (p11 leads to q13) segment of chromosome 2

Pericentric inversion of chromosome 2 was detected in four unrelated families. All these inversions involved the segment p11 leads to q13. The pedigree data are considered in comparison with other cases reported in the literature. Segregation data and possible reproductive failures are discussed.

Familial pericentric inversion 19

Several members in two families were found to have a pericentric inversion of chromosome 19. A review of four previous cases, together with those reported here, suggests that inversion of chromosome 19 is not related to the phenotypic features of the probands. Furthermore, there has been no report of an affected subject resulting from a duplication deficiency product of inverted chromosome 19 among the offspring of inversion heterozygotes. The suggested association of aneuploidy in the inversion carriers is also discussed.

Abnormal childhood phenotypes associated with the same balanced chromosome rearrangements as in the parents

Three patients have been detected because of abnormal phenotypes. Balanced chromosome rearrangements were found in their karyotypes, and in one of the parents in each case. In these three families the association of an abnormal phenotype and a balanced chromosome rearrangement may either be a chance happening or be induced by a submicroscopic loss of chromosome material, for which different position effects may be responsible, according to the case in question. These observations prompt us to ask what decision should be made relative to termination of pregnancy if such a rearrangement is found in amniotic cells in a family with a previous abnormal child.

Pericentric inversions inv(2)(p11q13) and inv(2)(p13q11) in 2 unrelated families

Pericentric inversions in chromosome 2 were traced in 2 unrelated North American black families. In the case of inv(2)(p13q11) no effect on reproduction was observed. In the case of inv(2)(p11q13) some reproductive abnormalities were noted which might be related to the inversion.

A fetus with recombinant of chromosome 8 inherited from her carrier father

A pericentric inversion of chromosome 8, inv(8)(p23q22), in a male carrier resulted in an unbalanced recombinant, rec(8)dup q, inv(8)(p23q22), which was diagnosed prenatally. The features seen in the aborted fetus resembled the features seen in a previously affected child who received the identical recombinant from her carrier mother. In this particular inversion involving chromosome 8, both male and female carriers risk producing an unbalanced progeny. Different familial pericentric inversions are reviewed for the presence or absence of unbalanced recombinants.

Familial pericentric inversion of chromosome 19, inv(19) (p13q13) with a note on genetic counseling of pericentric inversion carriers

An inmate of a hospital for the mentally retarded was found during a cytogenetic screening programme to have karyotype 46,XY,inv(19)(p13q13)mat. Clinical, cytogenetic and family findings are presented and it is concluded that the chromosomes abnormality was probably not the cause of the patient's retardation. The problem of genetic counseling of inversion carriers is examined in some detail and estimates of risk are given.