Volume 90 Number 5
Letters to the Editor
Sex chromosomal mosaicism undetected by prenatal study
Table | Tissue
Total cells
Karyotvpe
Skin (foreskin)
30
Skin (micropenis)
20
Testis
50
45,X in 19 (63%) 46,XY in II 45,X in 12 (60%) 46,XY in 8 45,X in 37 (74%) 46,XY in 13
To the Editor: Milunsky and Atkins' reported the occurrence of 46,XY/ 47,XXY mosaicism in a culture of amniotic fluid fibroblasts, but, on a repeat, confirmatory tap, all cells had a normal 46,XY karyotype. Because of the results of the second tap, the earlier mosaicism was considered to have arisen in culture; the pregnancy was continued and produced a phenotypically normal male. Subsequent chromosomal analysis of the infant's peripheral blood lymphocytes and skin fibroblasts confirmed the original sex chromosomal abnormality. A similar experience with 45,X/46,XY mosaicism was reported by Kardon and associates.-' In our experience with 114 consecutive amniocenteses, we have had an encounter with sex chromosomal mosaicism, but, in our patient, the anomaly was undetected antenatally. A 38-year-old mother of two healthy children, ages 6 and 18 years respectively, was advised by her physician to have amniocentesis for advanced maternal age, specifically for Down syndrome. Amniocentesis was performed at 15 weeks' gestation. Complete chromosomal analysis of 28 cells revealed a 46,XY karyotype: five more cells had 45 chromosomes, but none of these lacked a sex-chromosome. At birth, the newborn infant exhibited ambiguous genitalia. Chromosomal analysis of 50 peripheral blood Iymphocytes showed mosaicism, 45,X in 8 cells (16%) and 46,XY in 42 cells, Surgical considerations led to the selection of the female phenotype, and subsequently, the child has developed normally. Fibroblast cultures of skin from two sites and testis revealed high percentages of cells with monosomy X (Table l). Several months later fibroblasts from the original amniotic fluid cultures, which had been frozen for storage, were reestablished for additional studies. All 100 cells analyzed had a normal 46,XY karyotype. We believe that this is an example of the extreme selection of cells that may occur in amniotic fluid cell cultures. Because of the very high percentage of cells with monosomy X in the skin, one of the principal sources of cells in the amniotic fluid, our original chromosomal analysis should have readily detected the abnormality, if the 45,X cell type had been established in culture. Our follow-up study indicates that it apparently had not become established. In every amniotic fluid cell culture, we routinely analyze completely 25 to 30 or more cells in order to search specifically for mosaicism, According to Ford's calculations, :~ analysis of 30 cells should readily exclude the existence of a population of cells comprising 5 to 10% of the total population. Obviously, analysis of 100 ceils or even the selection of single colonies for karyotyping, as suggested by Sutherland and colleagues,' would not have beert informative in our case. We always insist on pretest counseling to inform women and their spouses of the limitations of amniocentesis and, in particular, our inability to exclude completely the possibility of chromosomal mosaicism. An awareness on the part of the prospective
84 1
parents of the pitfalls of prenatal diagnostic studies is essential in order to temper their reaction to an unexpected result.
Roger Ladda, M.D, Richard Hildebrandt, M.D, Yvonne Dobelle, B.A. Division of Genetics Department of Pediatrics and Division of Perinatal Medicine Department of Obstetrics~Gynecology Pennsr'lvania State University College of Medicine Hershey, PA 17033 REFERENCES I, 2,
3. 4.
Milunsky A, and Atkins L: Prenatal diagnosis of chromosomal mosaicism, Pediatrics 88:367, 1976. Kardon NB, Chernay PR, Hsu LY, Martin JL, and Hirschhorn K: Pitfalls in prenatal diagnosis resulting from chromosomal mosaicism, J PEDIATR 80:297, 1972. Ford CE: Mosaics and chimeras, Br Med Bull 25:104, 1969. Sutherland GR, Bowser-Riley SM, and Bain AD: Chromosomal mosaicism in amniotic fluid cell cultures, Clin Genet 7:400, 1975.
Recurrence of apparent de novo 21/21 translocation trisomy in a sibship To the Editor: We have observed a family with two of three children born with 21/21 translocation Down syndrome, whose parents have apparently normal karyotypes, with no evidence for mosaicism for a translocation carrier state. Both parents were 23 years old at the time of birth of their second child who had the typical stigmata of Down syndrome. A three-year-old daughter was normal physically and developmentally. The infant with Down syndrome was first seen at 10 months of age when he presented with developmental retardation, the stigmata of Down syndrome, and bilateral cryplor-
842
Letters to the Editor
chidism and micropenis. He died at age of 4 years following an episode of bronchopneumonia. Fifteen months after the birth of the first affected child, a brother was born after an uneventful pregnancy and delivery. Although amniocentesis was discussed with the parents, they declined this procedure. This infant also has the typical stigmata of Down syndrome, with severe psychomotor retardation and akinetic seizures. Cytogenetic studies on each of the children revealed identical karyotypes of 46,XY-21, +t(21q;21q). Studies of the parents revealed normal karyotypes in peripheral blood. The father was not available for a skin biopsy and examination of his dermatoglyphics. A skin biopsy from the mother revealed a normal 46,XX karyotype with no evidence for mosaicism. Her dermatoglyphics were normal, and discriminant analysis by the method of Deckers and associates 1 revealed a Hopkins score of-11.89, well within the limits of normal. The occurrence of a 21/21 translocation Down syndrome in two siblings could be explained on the basis of a balanced translocation carrier state in one of the parents. No evidence for such an abnormality, however, was noted. The birth of a normal child indicates that parental mosaicism for a translocation carrier state may account for the, findings. No chromosome abnormalities were identified, however, in either parent although lack of cooperation by the father precluded more intensive studies for such an aberration. There was no evidence for nonpaternity in this pedigree. In individuals mosaic for trisomy with no or few signs of Down syndrome the proportion of trisomic cells was found to be higher in skin fibroblast cultures.'-' Dermatoglyphic microsymptoms may also reflect mosaicism? 4 Unfortunately, these studies could not be carried out on the father. We are aware of only one previous report of multiple half-sibs with an apparent de novo G / G translocation Down syndrome whose mother is reported to have a normal karyotype.:'. "There is inadequate documentation, however, to rule out the possibility of maternal mosaicism for a cell line with a similar translocation. In cases of de novo translocation trisomy the question of amniocentesis arises because of possible increased risk for future progeny. Our experience suggests that the recurrence risk may be increased, and therefore amniocentesis in future pregnancies should be considered. Rina Schmidt, M.D. Harold M. Nitowsky, M.D. Department of Pediatrics Albert Einstein College of Medicine Bronx, N. Y. 10461 Aided by Grant from the National Institutes of Health-GM19100.
REFERENCES 1. Deckers JFM, Oorthuys AMA, and Doesburg WH: Dermatoglyphics in Down's syndrome I. Evaluation of discriminating ability of pattern areas, Clin Genet 4:311, 1973. 2. Richards BW: Investigation of 142 mosaic mongols and mosaic parents of mongols; cytogenetic analysis and maternal age at birth, J Ment Def Res 18:199, 1974.
The Journal of Pediatrics Mar 1977
3.
Penrose LS, and Smith GF: Down's anomaly, London, 1966, J. and A. Churchill Ltd. 4. Schmidt R, Dar H, and Nitowsky HM: Apparent parental mosaicism for trisomy 21 as a predisposing factor for children with Down's syndrome, in Armendares S, and Lisker R, editors: V International Congress of Human Genetics, Abstracts. 1976, City of Pabucato Excerpta Medica. 5. Behrman RE, Sigler AT, and Patchefsky AS: Abnormal hematopoieses in 2 of 3 siblings with mongolism, J PEDIATR 68:569, 1966. 6. Erratum: J PEDIATR 69:178, 1966.
13-year survival of a child with an untreated brainstem glioma To the Editor: It has been noted that the insidious onset, number, and variety of neurologic deficits, and the usual absence of increased intracranial pressure in patients with tumors of the brainstem may frequently mislead the physician. 1 We present a case which points out some of the pitfalls in the diagnosis of this tumor. CASE REPORT Patient G.M., a 3,822-gm male infant born following a normal pregnancy and two-hour labor, was felt to be normal until two months of age, when spontaneous jerky eye movements were noted. At seven months an ophthalmologist noted bilateral internal strabismus and spontaneous rotatory nystagmus. At 26 months, evaluation for delayed and awkward walking revealed flaccid dysarthria, spontaneous rotatory nystagmus, increased deep tendon reflexes, upgoing plantar responses, and broad-based clumsy gait. The sensory examination was normal, and he was felt to be of normal intelligence. The cerebrospinal fluid was normal, and pneumoencephalography showed a dilated posteriorly displaced fourth ventricle. The diagnosis of cerebral palsy with cerebellar hypoplasia and spastic quadriplegia was made. The neurologic deficits remained stable until age 10 when he noted increasing difficulty with function of bulbar muscles and in the use of his extremities. Re-examination at age 11 revealed an intelligent young man with jerking nystagmus on right lateral gaze and a very rapid pendular nystagmus on left lateral gaze, no papilledema, bilateral atrophy and fasciculation of the tongue, paralysis of the palate, weak atrophic hyperreflexic arms and hands, wasted very hyperreflexic lower extremities, and a normal sensory examination. A second pneumoencephalogram revealed posterior displacement of the fourth ventricle and at operation a low-grade astrocytoma was found involving the upper cervical cord and most of the brain stem. The patient died at age 13 3/12 years of respiratory failure. DISCUSSION It is estimated that 10 to 15% of primary intracranial neoplasms in children are brainstem gliomas. 2 The majority of these are fibrillary astrocytomas arising in order of frequency from the pons medulla and midbrain. The peak incidence is at age six
Letters to the Editor
Sex chromosomal mosaicism undetected by prenatal study
Table | Tissue
Total cells
Karyotvpe
Skin (foreskin)
30
Skin (micropenis)
20
Testis
50
45,X in 19 (63%) 46,XY in II 45,X in 12 (60%) 46,XY in 8 45,X in 37 (74%) 46,XY in 13
To the Editor: Milunsky and Atkins' reported the occurrence of 46,XY/ 47,XXY mosaicism in a culture of amniotic fluid fibroblasts, but, on a repeat, confirmatory tap, all cells had a normal 46,XY karyotype. Because of the results of the second tap, the earlier mosaicism was considered to have arisen in culture; the pregnancy was continued and produced a phenotypically normal male. Subsequent chromosomal analysis of the infant's peripheral blood lymphocytes and skin fibroblasts confirmed the original sex chromosomal abnormality. A similar experience with 45,X/46,XY mosaicism was reported by Kardon and associates.-' In our experience with 114 consecutive amniocenteses, we have had an encounter with sex chromosomal mosaicism, but, in our patient, the anomaly was undetected antenatally. A 38-year-old mother of two healthy children, ages 6 and 18 years respectively, was advised by her physician to have amniocentesis for advanced maternal age, specifically for Down syndrome. Amniocentesis was performed at 15 weeks' gestation. Complete chromosomal analysis of 28 cells revealed a 46,XY karyotype: five more cells had 45 chromosomes, but none of these lacked a sex-chromosome. At birth, the newborn infant exhibited ambiguous genitalia. Chromosomal analysis of 50 peripheral blood Iymphocytes showed mosaicism, 45,X in 8 cells (16%) and 46,XY in 42 cells, Surgical considerations led to the selection of the female phenotype, and subsequently, the child has developed normally. Fibroblast cultures of skin from two sites and testis revealed high percentages of cells with monosomy X (Table l). Several months later fibroblasts from the original amniotic fluid cultures, which had been frozen for storage, were reestablished for additional studies. All 100 cells analyzed had a normal 46,XY karyotype. We believe that this is an example of the extreme selection of cells that may occur in amniotic fluid cell cultures. Because of the very high percentage of cells with monosomy X in the skin, one of the principal sources of cells in the amniotic fluid, our original chromosomal analysis should have readily detected the abnormality, if the 45,X cell type had been established in culture. Our follow-up study indicates that it apparently had not become established. In every amniotic fluid cell culture, we routinely analyze completely 25 to 30 or more cells in order to search specifically for mosaicism, According to Ford's calculations, :~ analysis of 30 cells should readily exclude the existence of a population of cells comprising 5 to 10% of the total population. Obviously, analysis of 100 ceils or even the selection of single colonies for karyotyping, as suggested by Sutherland and colleagues,' would not have beert informative in our case. We always insist on pretest counseling to inform women and their spouses of the limitations of amniocentesis and, in particular, our inability to exclude completely the possibility of chromosomal mosaicism. An awareness on the part of the prospective
84 1
parents of the pitfalls of prenatal diagnostic studies is essential in order to temper their reaction to an unexpected result.
Roger Ladda, M.D, Richard Hildebrandt, M.D, Yvonne Dobelle, B.A. Division of Genetics Department of Pediatrics and Division of Perinatal Medicine Department of Obstetrics~Gynecology Pennsr'lvania State University College of Medicine Hershey, PA 17033 REFERENCES I, 2,
3. 4.
Milunsky A, and Atkins L: Prenatal diagnosis of chromosomal mosaicism, Pediatrics 88:367, 1976. Kardon NB, Chernay PR, Hsu LY, Martin JL, and Hirschhorn K: Pitfalls in prenatal diagnosis resulting from chromosomal mosaicism, J PEDIATR 80:297, 1972. Ford CE: Mosaics and chimeras, Br Med Bull 25:104, 1969. Sutherland GR, Bowser-Riley SM, and Bain AD: Chromosomal mosaicism in amniotic fluid cell cultures, Clin Genet 7:400, 1975.
Recurrence of apparent de novo 21/21 translocation trisomy in a sibship To the Editor: We have observed a family with two of three children born with 21/21 translocation Down syndrome, whose parents have apparently normal karyotypes, with no evidence for mosaicism for a translocation carrier state. Both parents were 23 years old at the time of birth of their second child who had the typical stigmata of Down syndrome. A three-year-old daughter was normal physically and developmentally. The infant with Down syndrome was first seen at 10 months of age when he presented with developmental retardation, the stigmata of Down syndrome, and bilateral cryplor-
842
Letters to the Editor
chidism and micropenis. He died at age of 4 years following an episode of bronchopneumonia. Fifteen months after the birth of the first affected child, a brother was born after an uneventful pregnancy and delivery. Although amniocentesis was discussed with the parents, they declined this procedure. This infant also has the typical stigmata of Down syndrome, with severe psychomotor retardation and akinetic seizures. Cytogenetic studies on each of the children revealed identical karyotypes of 46,XY-21, +t(21q;21q). Studies of the parents revealed normal karyotypes in peripheral blood. The father was not available for a skin biopsy and examination of his dermatoglyphics. A skin biopsy from the mother revealed a normal 46,XX karyotype with no evidence for mosaicism. Her dermatoglyphics were normal, and discriminant analysis by the method of Deckers and associates 1 revealed a Hopkins score of-11.89, well within the limits of normal. The occurrence of a 21/21 translocation Down syndrome in two siblings could be explained on the basis of a balanced translocation carrier state in one of the parents. No evidence for such an abnormality, however, was noted. The birth of a normal child indicates that parental mosaicism for a translocation carrier state may account for the, findings. No chromosome abnormalities were identified, however, in either parent although lack of cooperation by the father precluded more intensive studies for such an aberration. There was no evidence for nonpaternity in this pedigree. In individuals mosaic for trisomy with no or few signs of Down syndrome the proportion of trisomic cells was found to be higher in skin fibroblast cultures.'-' Dermatoglyphic microsymptoms may also reflect mosaicism? 4 Unfortunately, these studies could not be carried out on the father. We are aware of only one previous report of multiple half-sibs with an apparent de novo G / G translocation Down syndrome whose mother is reported to have a normal karyotype.:'. "There is inadequate documentation, however, to rule out the possibility of maternal mosaicism for a cell line with a similar translocation. In cases of de novo translocation trisomy the question of amniocentesis arises because of possible increased risk for future progeny. Our experience suggests that the recurrence risk may be increased, and therefore amniocentesis in future pregnancies should be considered. Rina Schmidt, M.D. Harold M. Nitowsky, M.D. Department of Pediatrics Albert Einstein College of Medicine Bronx, N. Y. 10461 Aided by Grant from the National Institutes of Health-GM19100.
REFERENCES 1. Deckers JFM, Oorthuys AMA, and Doesburg WH: Dermatoglyphics in Down's syndrome I. Evaluation of discriminating ability of pattern areas, Clin Genet 4:311, 1973. 2. Richards BW: Investigation of 142 mosaic mongols and mosaic parents of mongols; cytogenetic analysis and maternal age at birth, J Ment Def Res 18:199, 1974.
The Journal of Pediatrics Mar 1977
3.
Penrose LS, and Smith GF: Down's anomaly, London, 1966, J. and A. Churchill Ltd. 4. Schmidt R, Dar H, and Nitowsky HM: Apparent parental mosaicism for trisomy 21 as a predisposing factor for children with Down's syndrome, in Armendares S, and Lisker R, editors: V International Congress of Human Genetics, Abstracts. 1976, City of Pabucato Excerpta Medica. 5. Behrman RE, Sigler AT, and Patchefsky AS: Abnormal hematopoieses in 2 of 3 siblings with mongolism, J PEDIATR 68:569, 1966. 6. Erratum: J PEDIATR 69:178, 1966.
13-year survival of a child with an untreated brainstem glioma To the Editor: It has been noted that the insidious onset, number, and variety of neurologic deficits, and the usual absence of increased intracranial pressure in patients with tumors of the brainstem may frequently mislead the physician. 1 We present a case which points out some of the pitfalls in the diagnosis of this tumor. CASE REPORT Patient G.M., a 3,822-gm male infant born following a normal pregnancy and two-hour labor, was felt to be normal until two months of age, when spontaneous jerky eye movements were noted. At seven months an ophthalmologist noted bilateral internal strabismus and spontaneous rotatory nystagmus. At 26 months, evaluation for delayed and awkward walking revealed flaccid dysarthria, spontaneous rotatory nystagmus, increased deep tendon reflexes, upgoing plantar responses, and broad-based clumsy gait. The sensory examination was normal, and he was felt to be of normal intelligence. The cerebrospinal fluid was normal, and pneumoencephalography showed a dilated posteriorly displaced fourth ventricle. The diagnosis of cerebral palsy with cerebellar hypoplasia and spastic quadriplegia was made. The neurologic deficits remained stable until age 10 when he noted increasing difficulty with function of bulbar muscles and in the use of his extremities. Re-examination at age 11 revealed an intelligent young man with jerking nystagmus on right lateral gaze and a very rapid pendular nystagmus on left lateral gaze, no papilledema, bilateral atrophy and fasciculation of the tongue, paralysis of the palate, weak atrophic hyperreflexic arms and hands, wasted very hyperreflexic lower extremities, and a normal sensory examination. A second pneumoencephalogram revealed posterior displacement of the fourth ventricle and at operation a low-grade astrocytoma was found involving the upper cervical cord and most of the brain stem. The patient died at age 13 3/12 years of respiratory failure. DISCUSSION It is estimated that 10 to 15% of primary intracranial neoplasms in children are brainstem gliomas. 2 The majority of these are fibrillary astrocytomas arising in order of frequency from the pons medulla and midbrain. The peak incidence is at age six
