Common trisomy mosaicism diagnosed in amniocytes involving chromosomes 13, 18, 20 and 21: karyotype-phenotype correlations.

Karyotype-phenotype correlations of common trisomy mosaicism prenatally diagnosed via amniocentesis was reviewed in 305 new cases from a collaboration of North American cytogenetic laboratories. Abnormal outcome was noted in 10/25 (40%) cases of 47,+13/46, 17/31 (54%) cases of 47,+18/46, 10/152 (6.5%) cases of 47,+20/46, and in 49/97 (50%) cases of 47,+21/46 mosaicism. Risk of abnormal outcome in pregnancies with less than 50% trisomic cells and greater than 50% trisomic cells were: 26% (4/15) versus 60% (6/10) for 47,+13/46, 52% (11/21) versus 75% (6/8) for 47,+18/46, 4.5% (6/132) versus 20% (4/20) 47,+20/46, and 45% (27/60) versus 59% (22/37) for 47,+21/46. Phenotypically normal liveborns were observed with mean trisomic cell lines of 9.3% for 47,+13/46, 8.6% for 47,+18/46, 27% for 47, +20/46, and 17% for 47,+21/46. Cytogenetic confirmation rates were 46% (6/13 cases) for 47,+13/46 mosaicism, 66% (8/12 cases) for 47, +18/46, 10% (10/97 cases) for 47,+20/46, and 44% (24/54 cases) for 47,+21/46. There were higher confirmation rates in pregnancies with abnormal versus normal outcome: 50% versus 44% for 47,+13/46 mosaicism, 100% versus 33% for 47,+18/46, 66% versus 7% for 47, +20/46, and 55% versus 40% for 47,+21/46. Repeat amniocentesis is not helpful in predicting clinical outcome. It may be considered when there is insufficient number of cells or cultures to establish a diagnosis. Fetal blood sampling may have a role in mosaic trisomy 13, 18, and 21 as the risk for abnormal outcome increases with positive confirmation: 1/5 (20%) normal cases versus 5/8 (62%) abnormal cases. High resolution ultrasound examination(s) is recommended for clinical correlation and to facilitate genetic counselling.

Rare trisomy mosaicism diagnosed in amniocytes, involving an autosome other than chromosomes 13, 18, 20, and 21: karyotype/phenotype correlations.

In order to determine the significance of trisomy mosaicism of an autosome other than chromosomes 13, 18, 20, and 21, 151 such cases diagnosed prenatally through amniocentesis were reviewed. These rare trisomy mosaicism cases include 54 from 17 cytogenetic laboratories, 34 from a previous North American mosaicism survey, and 63 from published reports. All were cases of true mosaicism with information available on pregnancy outcome, and with no evidence of biased ascertainment. There were 11 cases of 46/47, +2; 2 of 46/47, +3; 2 of 46/47, +4; 5 of 46/47, +5; 3 of 46/47, +6; 8 of 46/47, +7; 14 of 46/47, +8; 25 of 46/47, +9; 2 of 46/47, +11; 23 of 46/47, +12; 5 of 46/47, +14; 11 of 46/47, +15; 21 of 46/47, +16; 7 of 46/47, +17; 1 of 46/47, +19; and 11 of 46/47, +22. As to the risk of an abnormal outcome, the data showed a very high risk (> 60 per cent) for 46/47, +2, 46/47, +16, and 46/47, +22; a high risk (40-59 per cent) for 46/47, +5, 46/47, +9, 46/47, +14, and 46/47, +15; a moderately high risk (20-39 per cent) for 46/47, +12; a moderate risk (up to 19 per cent) for 46/47, +7 and 46/47, +7 and 46/47, +8; a low risk for 46/47, +17; and an undetermined risk, due to lack of cases, for the remaining autosomal trisomy mosaics. Most cases were evaluated at birth or at termination, so subtle abnormalities may have escaped detection and developmental retardation was not evaluated at all. Comparison of the phenotypes of prenatally diagnosed abnormal cases and postnatally diagnosed cases with the same diagnosis showed considerable concordance. Since the majority of anomalies noted are prenatally detectable with ultrasound, an ultrasound examination should be performed in all prenatally diagnosed cases. In cytogenetic confirmation studies, the data showed much higher confirmation rates in cases with abnormal outcomes than in cases with normal outcomes [81 per cent vs. 55 per cent for fibroblasts (from skin, fetal tissue, and/or cord); 88 per cent vs. 46 per cent for placental cells; 22 per cent vs. 10 per cent for blood cells]. The confirmation rate reached 85 per cent when both fibroblasts and placental tissues were studied in the same case (with trisomic cells found in one or the other, or both). Therefore, one must emphasize that both fibroblasts and placental tissues should be studied. Except for 46/47, +8 and 46/47, +9, PUBS is of limited value for prenatal diagnosis of rate trisomy mosaicism. DNA studies for UPD are suggested for certain chromosomes with established imprinting effects, such as chromosomes 7, 11, 14, and 15, and perhaps for chromosomes 2 and 16, where imprinting effects are likely.

Prenatal diagnosis of a familial interchromosomal insertion of Y chromosome heterochromatin.

An apparently unbalanced karyotype containing an abnormal chromosome 11 was identified in a 16-week female fetus by analysis of cultured amniocytes. Fluorescence in situ hybridization (FISH) with a chromosome 11 paint identified the presence of an insertion in band 11q24. Parental karyotyping documented an unbalanced karyotype with the same der(11) chromosome in the phenotypically normal father. CBG-banding and FISH identified the insertion to be Yq12 heterochromatin: 46,XY, der(11)ins(11;Y)(q24;q12q12).ish der(11) (wcp11+,DYZ1+). The same der(11) chromosome was also found in the phenotypically normal paternal grandmother, demonstrating this additional Y chromosomal material did not affect normal female sexual development or fertility. The parents elected to continue the pregnancy and a normal girl was born at term, further confirming that this rare familial variant has no clinical significance. This case illustrates the importance of family studies, appropriate banding, and FISH analyses to accurately characterize apparent chromosomal abnormalities.

Prenatal cytogenetic results from cases referred for 44 different types of abnormal ultrasound findings.

During the period 1987 through mid-1993, 118 490 chromosome analyses from amniocytes were performed at the Integrated Genetics Laboratories in Santa Fe, New Mexico (formerly Vivigen Laboratories). This report summarizes the data for all specimens submitted because of anomalies seen during ultrasound examination; this includes 44 different categories of anomalies. There were 3177 cases referred because of at least one structural abnormality; 494 (15.5 per cent) of the cases had an abnormal karyotype. Our cytogenetic findings are summarized for the different types of anomalies and the corresponding empirical risks are given for abnormal cytogenetic results.

Cytogenetic analysis of 1375 amniotic fluid specimens from pregnancies with gestational age less than 14 weeks.

Our laboratory has received 1375 early amniotic fluid (EA) specimens during the past 5-year period for cytogenetics analysis. The gestational ages of the EA specimens were less than 14 weeks as estimated by ultrasound. The average volume of specimen received was 16 ml. Specimens were typically received in two collection tubes and cultured in Chang A and in supplemented MEM media using the in situ technique. Of the 1375 EA specimens received, 1356 were successfully cultured and yielded results. Abnormal results were found in 67 (4.9 per cent) of the cases. Nineteen specimens (1.4 per cent) failed to yield a result. The mean turn-around time (TAT) for all EA specimens was 8.28 days. In 1991, the average TAT for the EA specimens was 8.00 days compared with a TAT of 6.59 days for all specimens received over 14 weeks gestational age. The number of EA specimens received has increased from 1.5 per month in 1986 to 57 per month in 1991. In summary, our experience with EA specimens for cytogenetic analysis has demonstrated that the success rate is 98.6 per cent and that an increasing number of obstetricians are performing early amniocentesis as they seek to provide their patients with earlier results and an alternative to chorionic villus sampling.

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.

A liveborn infant with tetraploidy.

We report on an 22-month-old white girl with tetraploidy who is growing well, but who is extremely delayed in psychomotor development. When counseling parents it is important to realize that, although quite rare, tetraploid individuals can be born alive and live for at least 22 months. The implications are also relevant to prenatal diagnosis.

Trisomy 3p23----pter and monosomy 11q23----qter in an infant with two translocation carrier parents.

A newborn male infant with multiple congenital abnormalities was found to be trisomic for 3p23----pter and monosomic for 11q23----qter. His parents were both carriers of a balanced reciprocal translocation. Considerable overlap in phenotype-karyotype correlations was found between the two chromosomal syndromes in the patient.

Monosomy, trisomy, fragile sites, and rearrangements of chromosome no. 1 in a mentally retarded male with multiple congenital anomalies.

A 17-year-old male was referred for evaluation because of short stature and severe mental retardation. Major clinical findings included microphthalmia, micrognathia, low-set ears, a prominent beaked nose, clubbing of digits, and premature graying of hair. Cytogenetic analysis revealed a 45,XY,-1/46,XY/47,XY,+1 mosaicism in lymphocytic culture, a 45,XY,-1/46,XY mosaicism in skin fibroblasts, and fra(1p) sites in 2% of the metaphases from lymphocyte, fibroblast and bone marrow cultures. Post-zygotic non-disjunction causing this mosaicism is believed to be responsible for the patient's phenotype.

Prenatal diagnosis of inv(X)(q12q28) in a male fetus.

Amniocentesis and prenatal chromosome analysis were performed for advanced maternal age. The fetus was male with a paracentric inversion in the long arm of the X chromosome. The mother and a brother also carried the inversion. The pregnancy continued to term and the infant is developing normally at one year of age.

Ultrasound identification of apparently normal male genitalia in a 46,X,+mar fetus.

A level II ultrasound examination revealed a scrotum and penis in a fetus with a 46,X,+mar chromosome complement. The marker was subsequently considered to be a del(Y)(q11). A phenotypically normal male infant was born. Detailed ultrasound examination of similar cases for visualisation of the genitalia is recommended.

An infant with trisomy 6q21 leads to 6qter.

A female who died shortly after birth with multiple congenital anomalies corresponding to the clinical picture of partial 6q trisomy is described and the autopsy findings are presented. The patient had an unbalanced chromosome complement with a 6q21 leads to 6qter duplication. Her mother is a balanced 46,XX,t(6;10)(q21;q26) carrier.

Long survival in trisomy-13-syndrome: 21 cases including prolonged survival in two patients 11 and 19 years old.

The mean survival in Trisomy-13-syndrome patients is reported to be 130 days. We have diagnosed 21 cases of this syndrome in this institution (11 females and 10 males); 15 patients had regular trisomy 13 and 6 had translocation-trisomy 13 karyotypes. The mean survival of the 19 patients who died was 97.05 days; translocation patients survived longer than regular trisomy patients. The oldest living patients with trisomy 13 are a girl 19 and a boy 11 years old. Both are black, have regular trisomy 13 karyotypes and have had most of the manifestations of the syndrome. No mosaicism was detected in repeated cytogenetic studies. The 19-year-old patient is the oldest known living person with regular trisomy 13.

Brief clinical report: an infant with duplication of 17q21 lead to 17qter.

Duplication of the distal part of 17q has been reported in 4 patients [1,2]. We are reporting clinical, autopsy, and cytogenetic data on an additional patient whose condition was due to a familial translocation in which the patient's chromosome constitution is 46,XX, der(4),t(4;17)(p16;q21) pat. The phenotype of the five known patients with this duplication is very similar, and their manifestations are distinct enough to be clinically recognizable. Abnormalities common to all five patients are severe growth impairment, craniofacial anomalies with severe hypertelorism, frontal bossing and temporal narrowness, a widow's peak, narrow palpebral fissures, a thin upper lip overlapping a thin lower lip with down-turned corners of the mouth, micrognathia, apparently low-set and deformed ears, short webbed neck, and hyperlaxity of the limbs.

Family with three apparently balanced t(3;15) (p27;q22) translocation carriers. Association with deficits in language acquisition and mental retardation: a possible example of position effect in man.

A father, son, and daughter had a (3;15) (p27;q22) simple reciprocal translocation. No abnormality in the G-banding pattern was noted. The girl was most severely affected; she had an abnormal phenotype, noticeable delay in receptive and expressive language development, bilateral hearing impairment, and definite mental retardation. The boy had a moderate delay in receptive language skills, had moderate hearing impairment in one ear, and showed mild mental retardation. The father has low-set ears, some deficits in receptive language skills, is illiterate, and was found to be borderline mentally retarded. The mother and younger child do not have the translocation and are normal in terms of phenotype, intellect, and verbal skills. The accumulating evidence suggests that balanced translocations are associated with an increased frequency of intellectual deficit and congenital anomalies, and the cytogenetic mechanism may be that of position effect.

Chromosome analysis in cases with repeated spontaneous abortions.

G-banded chromosome complements were analyzed from couples and individuals who had experienced 3 unexplained spontaneous abortions. One woman was found to be a carrier of a t(13q14q) chromosome; all other subjects had normal-appearing karyotypes. Banded chromosome studies are recommended for couples with repeated abortions in the absence of any apparent cause.