Trisomy 2p: analysis of unusual phenotypic findings.

We present three probands with partial trisomies 2p21-23 due to ins(4;2)(q21;p21p23) pat, 2p23-pter due to t(2;4)(p23;q35)mat, and 2p21-pter due to t(2;11)(p21;q23.3)mat. More than 50 cases of partial trisomy 2p have been reviewed and some abnormalities, unusual for most other types of structural autosomal imbalance, have been found in patients with inherited forms of 2p trisomy and in their non-karyotyped sibs. Neural tube defects (anencephaly, occipital encephalocele, and spina bifida) were found in five probands and 4/6 affected non-karyotyped sibs. The only triplicated segment common to all was 2p24. Different forms of "broncho-pulmonary a/hypoplasia" (including two cases of lung agenesis) were described in four patients (overlapping triplicated segment was 2p21-p25). Three patients (with overlapping triplicated segment 2p23-p25) had diaphragmatic hernia. Abnormal rotation of the heart or L-transposition of large vessels (with or without visceral heterotaxia) was found in two infants (overlapping triplicated segment 2p23-p24). In two patients with common triplicated segment 2p22.3-p25, neuroblastoma has been described. The occurrence of all these defects may be explained either by the action of the same gene(s) mapped to 2p24 or by action of some independent factors located in different segments of the short arm. Although the latter hypothesis is much less probable, it can not be rejected at the present time. We propose the existence of a genetic system controlling surveillance of an abnormal embryo to explain the phenotypic differences between patients with the same imbalance within a family. In some "restrictive" combinations the abnormal embryos will die, although in "permissive" combinations they can survive.

Trisomy 17p11-pter: unbalanced pericentric inversion, inv(17)(p11q25) in two patients, unbalanced translocations t(4;17)(q27;p11) in a newborn and t(4;17) (p16;p11.2) in a fetus.

Three patients and one fetus with almost complete trisomy 17p due to familial rearrangements are described. Two patients followed unbalanced transmission of a familial pericentric inversion, and one patient and one fetus were due to unbalanced segregation of familial translocations. In the inversion family, another two patients with multiple malformations had died before chromosome examination could be performed. The pattern of congenital anomalies as revealed from eleven cases of trisomy 17p11-pter include as the most prominent features: prenatal growth retardation, microcephaly, downslanting palpebral fissures, small mouth, small mandible, poorly shaped ears, short and webbed neck, genital hypoplasia, clinodactyly of fingers, crowding of toes, a high incidence of congenital heart defects and hernias. Postnatal survival is short mainly in patients with congenital heart defects. From the age of about 6 years onward, clinical findings become more distinct, with some signs of Charcot-Marie-Tooth neuropathy (pes cavus, adducted thumbs, dorsiflexed hallux, camptodactyly and limitation of movements in different joints), and the nose gets narrow and sharp, with hypoplastic alae.

[Genetic counseling in cases of chromosome insertions]. / Geneticheskoe konsul'tirovanie pri khromosomnykh vstavkakh

The principles of the estimation of the risk of repeated birth of malformed child and spontaneous abortion in families of balanced carriers of insertions are presented. A risk for a carrier is formed from two parts: a risk for a carrier of reciprocal translocation and a risk for a carrier of insertion of the came length as inseried segment. The first component of the risk is a constant, the latter one is a variable. It depends on the length of the inserted segment, the type of its inclusion (direct or inverted) and sites of break points. An estimation of the risk in hypothetical insertion 46, XX, inv ins (4; 2) (q24; q22q34) is described as a model. The same method of counselling may be used for the families with triple translocations t(a-, b-, c+) with "insertion" of fragment of chromosome "a" between the parts of "b" and "c" chromosomes. A tentative empirical mean value of repeated birth of malformed child and spontaneous abortion in families with insertions is 29% and 45% for the female carrier, and about 37% and 25% for the male carrier.

[Genetics of Patau's syndrome (an analysis of 59 families)]. / Genetika sindroma Patau (analiz 59 semei).

Different parental translocations were observed in 11 out of 59 families where a child with Patau's syndrome was born. All cases, except for one with t(13; 18) (q14; q23) in the father, revealed the Robertsonian translocations. In most cases there were t(13; 14). The t(13; 15) and t(13; 13) translocations were detected in one mother each. The latter woman bore three babies with Patau's syndrome. One boy in this series had trisomy 13 and sporadic translocation t(2; 22) (q31; q13) simultaneously.

Partial trisomy 11q as the result of sporadic translocation.

Partial trisomy 11q due to a sporadic translocation was found in a mentally retarded girl with multiple abnormalities. The proportion of sporadic translocations involved in the total incidence of partial trisomies is discussed.

Genetics of the +p9 syndrome.

An analysis of data about the +p9 syndrome revealed that this clinical entity may occur in some different genetic forms. The recurrence risk in cases with familial translocations is due to the type of meiotic segregation, 2:2 or 3:1. It was shown a nonrandomness of involvement of chromosomes 15 and 22 in translocations with chromosome number 9.

Trisomy for the distal part of the short arm of chromosome 3.

A new case is presented of partial trisomy 3p in a one-year-old mentally retarded female infant with characteristic craniofacial dysmorphism and rare-faction of the stroma of the iris. The partial trisomy resulted from paternal balanced translocation t(3;6)(p25;p25). A review of the literature revealed that 1. both sexes are equally affected; 2. holoprosencephaly, found in 4 of 45 cases, may be considered the major and most severe anomaly of this syndrome; 3. the life-span of partial trisomy 3p is shorter than generally believed as most patients with severe malformations probably die before karyotype studies are initiated.

The Wolf-Hirschhorn syndrome. I. Genetics.

Four new cases of the Wolf-Hirschhorn syndrome are presented, two of which were due to t(4;22)mat. Review of the literature (more than 100 cases of the Wolf-Hirschhorn syndrome) showed that 13 % of all the reported cases were not mutations but segregations of parental chromosomal aberrations, primarily translocations. Similar data were obtained previously for other deletions (5p--, 18p--, 18q--). Analysis of data on some "new" deletion syndromes (4q--, 8p--, 9p--, 10p--, 11p--, 11q--) revealed that 14.5 % were inherited cases. Thus, all human autosomal deletions have virtually the same genetic pattern.

Trisomy 8p due to the 3:1 segregation of the balanced translocation t(8;15)mat.

An additional small G-like chromosome was found in a newborn female with multiple abnormalities and hemorrhagic diathesis. G banding showed that the index patient was trisomic for the short arm of chromosome 8 and revealed the anomaly t(8;15)(q12;p11) in her mother. The relationship between chromosome 8 and multiple hemorrhages is discussed.

Partial trisomy 10p in two generations.

Two cases of partial 10p trisomy due to a t(10;20)(p12;p12) in two generations of a family are presented. Analysis of 20 known cases of such aberrations confirmed the opinion of Schleiermacher et al. (1974) that partial trisomy 10p is a distinct clinically recognizable entity. The most important diagnostic features of this syndrome are dolichocephaly, prominent forehead, wide open sutures and fontanelles, broad root of the nose, cleft lip and palate, clubfoot, and cystic changes in kidneys.

Trisomy 20p: case report and genetic review.

Partial trisomy for the distal part of the short arm of chromosome 20 reported in a girl aged 11/2 years with typical craniofacial dysmorphies and psychomotor retardation. The trisomy resulted from a paternal translocation t(14;20) (q32.3;p11.1). The review of 25 cases of partial trisomy 20p showed that most cases (22 : 25) were due to parental translocations. Predominant involvement of small chromosomes in translocations with chromosome 20 was also detected.

Partial trisomy 5q and partial monosomy 5q within the same family.

The observation of partial trisomy for 5q31-5qter and partial monosomy for the same segment in two offspring within the same family is presented. Their normal mother was a balanced carrier of a reciprocal translocation 46,XX,t(5;10) (q31.3;q26). The trisomic female had craniofacial dysplasia, a short neck, clinodactyly of the 5th fingers, a small umbilical hernia, arhinencephalia, cerebellar hypoplasia, atrial septal defect, an accessory spleen, bifid uterus and vagina, hypoplastic ovaries. Potter syndrome with cystic dysplasia of the left kidney and agenesis of the right, urethral atresia, uterus unicornus with utero-urethral fistula, true hermaphroditism with two ovaries and one testicle were found in her stillborn sister. Analysis of the manifestations of monosomy 5q and trisomy 5q in the same family supports a well known fact that the effects of deletions are more pronounced than those of duplications for the same segments.