Partial trisomy 16q and partial monosomy 7p of a fetus derivated from paternal balanced translocation: A case report

INTRODUCTION

Subchromosomal deletions and duplications could currently be detected by noninvasive preliminary screening (NIPS). However, NIPS is a screening test that requires further diagnosis. Here we report a fetus with an autosomal abnormality revealed by NIPS and conventional karyotype combined with copy number variations sequencing (CNV-seq) confirmed the fetus with an unbalanced translocation.

PATIENT CONCERN

This was the fourth pregnancy of a 30-year-old woman who underwent 2 spontaneous abortions and gave birth to a child with a normal phenotype. The woman and her husband were healthy and nonconsanguineous. NIPS indicated a repeat of about 19-Mb fragment at the region of 16q22.1-q22.4 at 17-week gestation.

DIAGNOSES

The combination of traditional karyotype and CNV-seq could better locate the abnormal chromosomal region and further identify the source of fetal chromosomal abnormalities. Simultaneously, we evaluated the fetal morphology by ultrasound examination. The karyotype of the fetus was 46,XX,der(7)t(7;16)(p22;q23) and CNV-seq results showed an approximately 20.96-Mb duplication in 16q22.1-q24.3 (69200001-90160000) and an approximately 3.86-Mb deletion in 7p22.3-p22.2 (40001-3900000). Prenatal ultrasound revealed the fetal micrognathia. The paternal karyotype was 46,XY, t (7;16) (p22;q23), while the maternal was normal. The fetus inherited an abnormal chromosome 7 from its father.

INTERVENTIONS

No treatment for the fetus.

OUTCOMES

Pregnancy was terminated.

CONCLUSIONS

To our knowledge, the occurrence of de novo partial trisomy 16q (16q22.1-qter) and partial monosomy 7p (7p22.2-pter) has not previously been reported up to now. Here, we present the perinatal findings of such a case and a review of the literatures. CNV-seq combined with karyotype is a useful tool for chromosomal abnormalities indicated by NIPS.

Prenatal diagnosis of partial monosomy 21q (21q22.1→qter) associated with intrauterine growth restriction and corpus callosum dysgenesis

OBJECTIVE

A prenatal diagnosis of partial monosomy 21q(21q22.1→ qter) in fetus with intrauterine growth restriction and corpus callosum dysgenesis but escaped from the detection by cell free DNA testing was reported.

CASE REPORT

A 31-year-old, primigravida women, presented with intrauterine growth restriction and corpus callosum dysgenesis at 23 weeks of gestational age by anatomic ultrasound screening. The interphase fluorescence in situ hybridization (FISH) analysis on amniocytes revealed monosomy 21, while the cytogenetic analysis and array comparative genomic hybridization (CGH) with CytoScan gene chip ascertained a 12.35 Mb deletion at 21q22.1q22.3.

CONCLUSION

Although noninvasive prenatal testing is used extensively and can be applied to certain microdeletion diseases, the application for uncommon deletion disorders such as the present case remains limited. Prenatal examination with detailed ultra-sonography combined with different modalities of invasive prenatal testing can provide a more comprehensive information.

A rare case of monosomy 18p: translocation between chromosomes 18 and 21

A rare case of monosomy 18p with molecular cytogenetic characterization of 18;21 whole arm translocation is presented. An 8-year-old gril with mental deficiency and growth deficiency was the child of a 45-year-old healthy mother and 50-year-old nonconsanguineous father with unremarkable prenatal history. She had a round face, flat nasal bridge, micrognathia and hypotonia. Cytogenetic studies revealed de novo 45,XX,del(18)t(18;21) karyotype, which was confirmed by fluorescence in situ hybridization (FISH).

Prenatal detection of full monosomy 21 in a fetus with increased nuchal translucency: molecular cytogenetic analysis and review of the literature

Full monosomy 21 is an extremely rare chromosomal disorder. A 38-year-old woman attended a first trimester scan. Ultrasound (U/S) imaging of the fetus at 12 weeks of gestation showed features of increased nuchal translucency measurement (12 mm). Chorionic villi sampling (CVS) was performed after genetic counseling. At 16 weeks of gestation the fetus showed U/S characteristics of severe intrauterine growth restriction, generalized edema and hydrothorax. Cytogenetic examination was performed using quantitative fluorescent polymerase chain reaction analysis, standard Giesma banding and fluorescent in situ hybridization analysis. Non-mosaic full monosomy 21 was detected and the parents opted to terminate the pregnancy. Microsatellite analysis demonstrated maternal origin of the single chromosome. This case represents one of the few cases of prenatally diagnosed full monosomy 21 confirmed only by CVS, in which the parental origin of the single chromosome was determined.

Primary amenorrhoea in a patient with mosaicism for monosomy X and a derivative X-chromosome

Primary amenorrhoea is defined as the absence of menstruation in phenotypic women aged 16 years or older, if secondary sexual characteristics are present. X chromosome abnormalities probably comprise about one half of all cases, including Turner syndrome and X chromosome rearrangements. Conventional banding cytogenetic methods might miss the accurate detection of structural chromosome abnormalities. The fluorescence in situ hybridization (FISH) and multicolor FISH techniques are required to interpret specific chromosomal rearrangement. As far as we know, we report the first case with chromosome mosaicism for monosomy X and terminal deletion of Xq26 with duplication of Xp11-->pter. In spite of the fact that a 45,X karyotype was detected in 46% of lymphocytes, she was tall and her secondary sexual characteristics were moderately developed, including breast, pubic and axillary hair stages. Cytogenetic and FISH analyses should be considered for patients presenting primary amenorrhoea even if there are no other clinical features suggestive of chromosome abnormality.

FISH and SNP-A karyotyping in myelodysplastic syndromes: improving cytogenetic detection of del(5q), monosomy 7, del(7q), trisomy 8 and del(20q)

Cytogenetic aberrations identified by metaphase cytogenetics (MC) have important diagnostic, prognostic and therapeutic roles in myelodysplastic syndromes (MDS). Fluorescence in situ hybridization (FISH) complements MC by the ability to evaluate large numbers of both interphase and metaphase nuclei. However, clinically practical FISH strategies are limited to detection of known lesions. Single nucleotide polymorphism array (SNP-A)-based karyotyping can reveal unbalanced defects with superior resolution over MC and FISH and identify segmental uniparental disomy (UPD) undetectable by either method. Using a standardized approach, we focused our investigation on detection of -5/del(5q), -7/del(7q), trisomy 8 and del(20q) in patients with MDS (N=52), MDS/myeloproliferative overlap syndromes (N=7) and acute myeloid leukemia (N=15) using MC, FISH and SNP-A karyotyping. The detection rate for del(5q) was 30, 32 and 32% by MC, FISH, and SNP-A, respectively. No single method detected all defects, and detection rates improved when all methods were used. The rate for detection of del(5q) increased incrementally to 35% (MC+FISH), 38% (MC+SNP-A), 38% (FISH+SNP-A) and 39% (all three methods). Similar findings were observed for -7/del(7q), trisomy 8 and -20/del(20q). We conclude that MC, FISH and SNP-A are complementary techniques that, when applied and interpreted together, can improve the diagnostic yield for identifying genetic lesions in MDS and contribute to the better description of abnormal karyotypes.

Monosomy 18p presenting with holoprosencephaly and increased nuchal translucency in the first trimester: report of 2 cases

OBJECTIVE

The purpose of this series is to describe the first-trimester sonographic findings leading to the diagnosis of monosomy 18p.

METHODS

The sonographic appearance of 2 cases of monosomy 18p, detected as part of first-trimester sonographic screening for aneuploidy at this institution, was reviewed.

RESULTS

Increased nuchal translucency thickness, alobar holoprosencephaly, and facial defects were detected in both cases. Chromosomal analysis by chorionic villus sampling revealed de novo del(18p) in 1 case and monosomy 18p as the result of an 18q isochromosome in the other.

CONCLUSIONS

Increased nuchal translucency thickness in association with brain and face anomalies on a first-trimester scan allowed the early diagnosis of monosomy 18p. Fetuses with holoprosencephaly can be readily identified in the first trimester by examining a cross section of the fetal head looking for the "butterfly" sign. Prenatal karyotyping provides important information regarding the etiology and risk of recurrence in these cases.

High-density genome array is superior to fluorescence in-situ hybridization analysis of monosomy 3 in choroidal melanoma fine needle aspiration biopsy

PURPOSE

Using fluorescence in situ hybridization (FISH) and high-density single nucleotide polymorphism (SNP) mapping genome array, we comparatively evaluated chromosome 3 status and other chromosomal aberrations within a series of choroidal melanomas biopsied by fine needle aspiration (FNAB).

METHODS

Transscleral FNAB was performed in 59 patients (59 eyes) who had a clinical diagnosis of choroidal melanoma. Biopsies were processed for chromosome 3 status by centromeric interphase FISH, cytopathology, cell culture, and simultaneous genomic DNA and RNA mapping array analysis.

RESULTS

FISH yielded chromosome 3 status in 38 of 59 (64%) eyes, while high-density SNP mapping array yielded chromosome 3 status in 43 of 59 (73%) eyes. Monosomy 3 was detected by FISH in 15 of 38 (39%) cases, and high-density SNP mapping array data confirmed the finding in 13 of the 15 cases. Furthermore, high-density SNP mapping array revealed five additional cases of significant chromosome 3 aberration not detected by FISH. High-density genomic mapping also provided detailed patterns of chromosomal gain and loss on chromosomes 1, 6, 8, and 9 which segregated into two groups characterized by either monosomy 3 or chromosome 6p gain.

CONCLUSIONS

High-density SNP mapping array was better than FISH in detecting chromosome 3 aberrations and monosomy in our melanoma samples. More importantly, the mapping arrays detected additional patterns of chromosomal aberration, which suggest specific pathways for cytogenetic rearrangements in choroidal melanoma and may improve prognostic testing.

[Diabetes insipidus revealing chronic myelomonocytic leukemia]

INTRODUCTION

Central diabetes insipidus is most frequently reported to occur after a trauma from surgery or accident. However, between 30 and 50% of cases are considered idiopathic. It's a rare complication of myelodysplastic syndrome.

CASE REPORT

A 61-year-old patient presented central diabetes insipidus revealing, 17 months before, chronic myelomonocytic leukemia. Cytogenetics studies revealed monosomy 7. Acute myeloid leukemia appears 3 months after training rapid patient's death.

DISCUSSION

Blood examination is necessary before to conclude idiopathic central diabetes insipidus. The discovery of chronic myelomonocytic leukemia implicates a rapid managing before its possible acute myeloid leukemia transformation. Indeed, prognosis of central diabetes insipidus and acute myeloid leukemia associated, in presence of monosomy 7, is very poor.

Atypical teratoid/rhabdoid tumor of the spine in an adult: case report and review of the literature

Atypical teratoid/rhabdoid tumors (AT/RTs) are rare, malignant brain tumors which occur almost exclusively in infants and young children. There have been only 17 cases of AT/RT in adults reported in the medical literature and the rarity of this tumor makes the diagnosis in adults difficult. We describe a case of an AT/RT of the spinal cord in an adult. A 43-year old woman presented with neck and left upper extremity pain. An MRI demonstrated a mass lesion in the dorsal spinal cord extending from C4 to C6. The patient underwent a C3 through C7 laminectomy. In consultation with senior pathologists at other institutions, the lesion was initially diagnosed as a rhabdoid meningioma. Molecular genetic studies revealed monosomy 22 and loss of expression of the INI1 gene in 22q11.2. Subsequently, immunohistochemical studies revealed the absence of INI1 gene expression in the malignant cells, supporting the diagnosis of AT/RT. The patient underwent three additional surgical procedures for recurrent disease throughout the neuraxis secondary to leptomeningeal spread of the tumor. Despite aggressive surgical resection, adjuvant chemotherapy and radiation therapy, the patient succumbed to the disease two and a half years after her initial presentation. An unrestricted autopsy was performed. To our knowledge, this is the first case of a spinal atypical teratoid/rhabdoid tumor in an adult fully documented with molecular, immunohistochemical, cytogenetic and autopsy findings.

Subtelomeric analysis detects a familial 10p;12p rearrangement in two relatives with a distinct syndrome

In recent years, subtelomeric rearrangements have been identified as a major cause of multiple congenital anomalies (MCA)/mental retardation (MR) syndromes. Currently, more than 2,500 individuals with MR have been tested and subtelomeric rearrangements were detected in about 6%. Therefore, subtelomeric FISH analysis is indicated as a second tier test after high-resolution G-banding analysis, in subjects with otherwise unexplained developmental delay/MR and/or MCA. We describe a female patient and her maternal aunt, both showing a distinct phenotype, associated with the same complex subtelomeric rearrangement. Subtelomeric FISH testing performed between 1 year 9 months and 20 years after the initial karyotype showed, in both patients, distal trisomy 12p and distal monosomy 10p as follows: 46,XX.ish der(10)t(10;12)(p15.3;p13.31). Parental subtelomeric FISH analysis showed the proposita's mother (sister of Patient 2) and grandmother (mother to Patient 2), to have a balanced 10p:12p translocation. Both girls showed a similar phenotype with pre/postnatal growth retardation, moderate-to-severe developmental delay/MR, very poor/absent speech, hypotonia, lax ligaments, and a distinct pattern of malformation. On examination there were blepharophimosis; bilateral ptosis/epicanthus; broad, depressed nasal bridge with a beaked nose; short philtrum; low-set, posteriorly rotated, overfolded ears; micrognathia; mild webbing of the neck; mild broadening of thumbs; puffy hands/feet; long hallux; and sacral/coccygeal dimples. A slow overall improvement was seen in both patients over time. To our knowledge, a complex subtle rearrangement as the one seen in our patients has not been reported thus far. Our patients show features of partial 10p deletion syndrome rather than those of partial duplication 12p, confirming the general rule that deletions are more phenotypically penetrant than duplications.

Monosomy 7 as the sole abnormality of an acute basophilic leukemia

We report the case of a 72-year-old man who had the very rare disease acute basophilic leukemia with the sole chromosomal finding of a monosomy 7. Most nuclear cells in the peripheral blood and bone marrow samples were either basophils or blasts. The blasts showed negative reaction with myeloperoxidase, periodic acid Schiff, chloroacetate esterase, alpha-naphthyl butyrate esterase, acid phosphatase, and Sudan black B. Metachromatic features of the blasts, however, were observed with toluidine blue stain. Electron microscopic evaluation showed the typical ultrastructure, with basophil and immature mast cell granules. Cytogenetic study revealed monosomy 7 in all metaphase cells, and this finding was confirmed by fluorescence in situ hybridization. The Philadelphia chromosome was absent. Review of the literature revealed abnormalities in cases of ABL. To our knowledge, the case reported here is the first to have basophilic leukemia with monosomy 7 as the only chromosome abnormality.

Prenatal diagnosis and prenatal imaging features of fetal monosomy 1p36

Deletion of the distal end of the short arm of chromosome 1 (1p36) is thought to be a common terminal chromosomal deletion. However, few cases prospectively diagnosed prenatally have been reported. In this case, prenatal ultrasound at 21 weeks of gestation noted the fetus to have mild ventriculomegaly (Vhanterior = 11 mm and Vhposterior = 12 mm) and increased nuchal edema (6 mm). Maternal serum alpha-fetoprotein was normal unlike in a majority of previously described cases. The prenatal ultrasound features were further clarified with fetal MRI. Chromosome analysis following amniocentesis demonstrated a 1p36 deletion, which was confirmed by fluorescence in situ hybridization (FISH). The syndrome associated with 1p36 deletion is well described in infants and is characterized by typical facial features (prominent forehead, straight eyebrows. deep-set eyes, flat nasal bridge and a pointed chin). Other associated features are neurodevelopmental delay, seizures, cardiomyopathy and neurosensory hearing impairment. This case supplements our knowledge of the prenatal features of 1p36. Identification of this deletion by direct chromosomal analysis can be technically difficult and vigilance is required to improve diagnosis. FISH analysis is an important diagnostic adjunct where the diagnosis is suspected following classical G-banding techniques. However, in this chromosomal anomaly there remain few characteristic prenatal signs that are readily diagnosed with prenatal imaging.

[Selected problems of the diagnosis of Turner's syndrome]

Turner's syndrome (TS) can be diagnosed in one out of 2130 females. The aim of the current study was to collect data about circumstances associated with the diagnosis of the syndrome. The material consisted of 177 female patients from the whole Polish territory, that turned to the out-patient Clinic for Women with Turner's syndrome, Specialist Hospital No 2 Bytom. Patients underwent physical examination and all relevant clinical information were analysed. The mean age when the abnormal symptoms were found was 8.5 years. Only 50% of those, who first turned their attention to these symptoms, were the health care workers. The initial symptoms were quite variable. Classical symptoms, i.e. short stature and amenorrhea were present respectively in only 41% and 8% of patients. In 16% of patients the diagnosis was significantly delayed, because, due to a lack of symptoms TS was not suspected. The latest cases were diagnosed at the age of 14.6 +/- 8.2 years. When it came to analysing karyotypes, simple chromosome X monosomy was present in 56% of patients and in 24% of cases mosaic karyotypes were found. Studies were performed in 14 cities in Poland.

CONCLUSIONS

1. In most cases diagnosis of TS was markedly delayed. 2. More efforts are required in order to perform karyotype studies in younger patients then it is now. Also molecular studies should become more easily available, since they are a necessary supplement to cytogenetic studies.

Glioblastomatous recurrence of oligodendroglioma remote from the original site: a case report

BACKGROUND

As in all diffuse gliomas, recurrence is an inherent feature of oligodendrogliomas, either as the same or higher grade neoplasm at the primary site. The rate of remote recurrence after surgery for the primary tumor cannot be estimated from the scarce literature, but delayed treatment of the primary tumor and genetic alterations may be associated with this phenomenon.

CASE DESCRIPTION

A 40-year-old man presented with generalized seizures. A magnetic resonance imaging scan disclosed a right frontal mass lesion showing features of a low-grade glioma for which he refused any treatment. Seven months after diagnosis upon uncontrollable seizures, he underwent a stereotactic biopsy, which was followed by a right frontal craniotomy, both of which confirmed the lesion as a grade 2 oligodendroglioma. Six months after surgery, the patient presented with a left frontal lobe GBM without evidence of recurrence at the primary site. The genetic analysis of the primary and recurrent tumors showed trisomy 7, monosomy 10, but not 1p or 19q deletions, which have been proposed as markers for favorable prognosis.

CONCLUSION

Recurrence of a frontal lobe oligodendroglioma remote from the primary site as a GBM is a rare occurrence. Single-cell invasion across the corpus callosum with subsequent or simultaneous malignant degeneration into a secondary GBM is the likely mechanism. As the genetic analysis suggests, conversion of oligodendroglioma to GBM may be associated with gain of chromosome 7, loss of chromosome 10, and other genetic markers that may represent late events in the oncogenesis of oligodendroglial tumors.

Early and rapid prenatal diagnosis of monosomy 2q36.1 in trophoblast cells

OBJECTIVES

CVS is the earliest procedure for cytogenetic analysis but the quality of metaphases obtained does not allow the characterization of subtle chromosomal anomalies. We report the application interphase fluorescence in situ hybridization for the rapid prenatal diagnosis of a subtle structural chromosome anomaly in trophoblast cells.

METHODS AND RESULTS

The foetus was karyotyped because of a paternal complex chromosomal anomaly 46,XY,inv(2)(q14.3q35),ins(10;2)(q25;q36.1q36.1). Fluorescence in situ hybridization analyses were performed on interphase nuclei and metaphase chromosomes from uncultured chorionic villi using bacterial artificial chromosomes specific for the 2q chromosomal region. Direct conventional cytogenetics showed an apparently normal male karyotype, whereas fluorescence in situ hybridization analysis showed a deletion of the chromosomal region 2q36.1 and a paracentric inversion of the chromosome 2q leading to a partial monosomy 2q36.1.

CONCLUSION

This strategy allowed us to offer an early and rapid chromosomal analysis for this couple leading to a better management of the pregnancy. This report demonstrates that interphase fluorescence in situ hybridization can be used in direct CVS for a rapid and early prenatal diagnosis of complex chromosomal rearrangements.

Cryptic mosaicism for monosomy 20 identified in renal tract cells

We report a post-natal case of mosaic aneuploidy for chromosome 20 in a 4 months old male baby with an abnormal phenotype including dysmorphic features (asymmetric facial growth), ventricular septal defect, hypotonia and bilateral vesicoureteric reflux. Conventional cytogenetics on peripheral blood showed 1 cell of 200 with 47,XY,+20. Further investigations using fluorescent in situ hybridization (FISH) on a urine sample, with a centromere probe for chromosome 20, revealed 39 of 50 cells giving one signal indicative of monosomy 20. FISH analysis of a buccal smear was consistent with disomy 20 as was conventional cytogenetics on skin fibroblasts. This is the fourth reported case of mosaic monosomy 20, the second case where monosomy 20 is present with a trisomy 20 cell and the first case with each aneuploidy found in two separate tissues. The identification of mosaicism is a difficult task since the abnormal cells can be present only in certain tissues and may disappear with selection as the fetus develops, thus leading to single-cell abnormalities that may get dismissed (pseudomosaicism). The use of FISH in this case was crucial in identifying the cryptic mosaic monosomy 20 cell line. The likely mechanism of origin is post-zygotic nondisjunction giving rise to monosomy, disomy and trisomy cell(s) in the same or different tissues. Although no other trisomy 20 cells were found, the abnormal phenotype plus the finding of a monosomy 20 cell line make this mechanism the most plausible explanation. Had we dismissed the single-cell abnormality, the cryptic mosaicism of monosomy 20 would not have been identified. A detailed analysis of all tissues accessible in conjunction with careful consideration of all clinical information available is the best course of action in suspected mosaicism.

Unbalanced chromosomal translocation: a cause of recurrent spontaneous abortion

Recurrent spontaneous abortion, defined as three consecutive abortions, occurs in approximately 1% to 2% of couples. Although the cause is unknown in up to 50% of cases, about 5% of these couples are found to be a balanced translocation carrier. We report a case in which the mother was identified to be a translocation carrier following the birth of a baby with multiple congenital abnormalities.

Atypical meningioma in Werner syndrome: a case report

INTRODUCTION

Werner Syndrome, or adult progeria, is a rare autosomal recessive disorder caused by a mutation in the Werner Syndrome Gene belonging to the family of RecQ helicase. Malignant mesenchymal tumours and atherosclerosis are typical causes of death. Intracranial meningiomas are frequently described in these patients.

CLINICAL PRESENTATION

We present the case of a 46-year-old man with Werner Syndrome and a convexity meningioma. The patient had a 2-year history of paresthesia and paresis in his right leg, which had worsened in recent months. He underwent surgery with Simpson grade II removal, with improvement of the slight paresis and no other neurological defects. The patient then underwent radiotherapy (60 Gy). Histological examination revealed an atypical meningioma. Cytogenetic analysis showed a hypodiploid clone with a complex karyotype characterized by monosomy 22 and deletion 1p. After 3 years' follow-up no relapses had occurred.

CONCLUSION

1p deletion correlates with meningioma progression and in this case correlates with histological examination. The chromosomal instability underlying Werner Syndrome could have fostered the complex karyotype.

De novo monosomy 9p24.3-pter and trisomy 17q24.3-qter characterised by microarray comparative genomic hybridisation in a fetus with an increased nuchal translucency

OBJECTIVES

Increased nuchal translucency (NT) during the first trimester of pregnancy is a useful marker to detect chromosomal abnormalities. Here, we report a prenatal case with molecular cytogenetic characterisation of an abnormal derivative chromosome 9 identified through NT.

METHODS

Amniocentesis was performed because of an increased NT (4.4 mm) and showed an abnormal de novo 46,XX,add(9)(p24.3) karyotype. To characterise the origin of the small additional material on 9p, we performed a microarray comparative genomic hybridisation (microarray CGH) using a genomic DNA array providing an average of 1 Mb resolution.

RESULTS

Microarray CGH showed a deletion of distal 9p and a trisomy of distal 17q. These results were confirmed by FISH analyses. Microarray CGH provided accurate information on the breakpoint regions and the size of both distal 9p deletion and distal 17q trisomy. The fetus was therefore a carrier of a de novo derivative chromosome 9 arising from a t(9;17)(p24.3;q24.3) translocation and generating a monosomy 9p24.3-pter and a trisomy 17q24.3-qter.

CONCLUSION

This case illustrates that microarray CGH is a rapid, powerful and sensitive technology to identify small de novo unbalanced chromosomal abnormalities and can be applied in prenatal diagnosis.

Prenatal diagnosis in human immunodeficiency virus-infected women: a new screening program for chromosomal anomalies

OBJECTIVE

This study was undertaken to describe a new prenatal diagnosis program among human immunodeficiency virus (HIV)-infected women, and the perinatal outcome of this program's application over a more than 2-year period.

STUDY DESIGN

From June 2000 to December 2003, all HIV-infected women who were booked into the antenatal clinic before 20 weeks were offered a screening for chromosomal anomalies, with midtrimester amniocentesis in the tests that were positive.

RESULTS

A total of 116 pregnancies (including 3 sets of twins) were seen: 96 women were offered and accepted screening for chromosomal anomalies. Thirteen pregnancies had a positive screening test and amniocentesis was performed in 10 at median 16.5 gestational weeks: a trisomy 21 and a monosomy X were diagnosed. No vertical transmissions were documented by age 6 months in the 6 liveborn infants who underwent amniocentesis.

CONCLUSION

A program of prenatal diagnosis for chromosomal anomalies appears to be effective when applied to HIV-infected women, although safety remains to be proven.

Genetic testing in the myelodysplastic syndromes: molecular insights into hematologic diversity

The myelodysplastic syndromes (MDS) are associated with a diverse set of acquired somatic genetic abnormalities. Bone marrow karyotyping provides important diagnostic and prognostic information and should be attempted in all patients who are suspected of having MDS. Fluorescent in situ hybridization (FISH) studies on blood or marrow may also be valuable in selected cases, such as patients who may have 5q- syndrome or those who have undergone hematopoletic stem cell transplantation. The MDS-associated cytogenetic abnormalities that have been defined by karyotyping and FISH studies have already contributed substantially to our current understanding of the biology of malignant myeloid disorders, but the pathobiological meaning of common, recurrent chromosomal lesions such as del(5q), del(20q), and monosomy 7 is still unknown. The great diversity of the cytogenetic findings described in MDS highlights the molecular heterogeneity of this cluster of diseases. We review the common and pathophysiologically interesting genetic abnormalities associated with MDS, focusing on the clinical utility of conventional cytogenetic assays and selected FISH studies. In addition, we discuss a series of well-defined MDS-associated point mutations and outline the potential for further insights from newer techniques such as global gene expression profiling and array-based comparative genomic hybridization.

Prenatal Diagnosis of a Partial Monosomy 7q11→q31 in a Fetus with Split Foot

OBJECTIVE

A 27-year-old woman was referred to our laboratory for genetic counseling at 26 weeks of gestation due to abnormal ultrasound findings including intrauterine growth retardation, Dandy-Walker malformation and lower extremity anomalies.

METHODS

Chromosome analysis was performed on fetal blood sample obtained by cardiocentesis.

RESULT

We observed an abnormal karyotype with a structural abnormality of the long arm of chromosome 7. Both parents' chromosomes were normal; thus, the fetal karyotype designation was 46,XX, del(7)(pter-->q11::q31-->qter) de novo. Skin biopsy sample was taken to confirm the karyotype after therapeutic abortion was performed. The result was identical. Postmortem examination and autopsy showed facial dysmorphism, malformations of the lower extremities and central nervous system anomalies.

CONCLUSION

7q interstitial deletions cause a wide spectrum of congenital abnormalities and syndromes linked to the deleted segments. Our case had a rather wide chromosome region deleted and it is important, because prenatal diagnosis was performed. Thus, the family had the chance to evaluate the situation and decided to terminate the pregnancy after genetic counseling.

[Cervical origin of the subclavian artery: echocardiographic diagnosis in patients with monosomy 22q11]

OBJECTIVE

To assess the sensitivity and specificity of echocardiography in the detection of anomalies of the subclavian artery (cervical origin, aberrant origin from the descending aorta or isolation) in patients with monosomy 22q11.

METHOD

From 1/1998 until 03/2002 we examined 57 patients with conotruncal cardiac malformations. 30 patients had pulmonary atresia and ventricular septal defect (53 %), 13 interrupted aortic arch (23 %), 9 tetralogy of Fallot (16 %) and 5 common truncus arteriosus (9 %). Echocardiographic examination included identification of the laterality of the aortic arch as well as examination of the origin of the brachiocephalic vessels. The results were compared with angiographic and intraoperative findings. Median age at echocardiographic investigation was 74 days (range 1 d - 33.4 yrs.).

RESULTS

Laterality of the aortic arch was assessed correctly in all patients. 20/57 patients had a right-sided aortic arch (35 %). Echocardiography detected all anomalies of the subclavian artery (14/57 patients, 25 %, sensitivity 100 %) and excluded these anomalies correctly in 43 patients (specificity 100 %). Exact classification of the anomaly of the subclavian artery was possible in 6/6 patients with a cervical origin of the artery and in 7/8 patients with aberrant origin from the descending aorta. Monosomy 22q11 was diagnosed in 21 patients (37 %).

CONCLUSION

Echocardiography achieves a high sensitivity in the detection of anomalies of the subclavian artery. The diagnosis of cervical origin of the artery, in particular, can be easily established. As this anomaly appears to be a specific marker for monosomy 22q11, echocardiography facilitates reliable identification of these patients in clinical practice.

Genotype/phenotype correlation in a patient with partial monosomy 15 and partial trisomy 14

We report on a girl with severe mental and psychomotor retardation caused by an unusual, unbalanced translocation t(14;15) of maternal origin. The unbalanced translocation in the patient resulted in trisomy 14pter-->q13 and monosomy 15pter-->q11.2. In addition to common features described in other patients with small proximal trisomies of chromosome 14, our patient presented with hypopigmented skin with light hair and eye color and severe speech impairment. Therefore the phenotype of the girl shows few similarities to that of Angelman syndrome patients, although the breakpoint in chromosome 15 in our patient was found to be proximal to the PWS/AS region.

Prenatal diagnosis of monosomy 4p14→pter and trisomy 11q25→qter: clinical presentations and outcomes

We present the case of a pregnant woman with low free beta-HCG in maternal serum Down syndrome screening that led to prenatal diagnosis of a fetus with 46,XY,der(4)t(4;11)(p14; q25). This chromosomal aneuploidy resulted from unbalanced segregation of a paternal balanced translocation, t(4;11)(p14;q25). Prenatal ultrasound revealed intrauterine growth restriction, cleft lip and palate, a thick nuchal fold, a single umbilical artery, and pyelectasis. Array-based comparative genomic hybridization and short tandem repeat markers further located the exact breakpoint of translocation. The woman had her pregnancy terminated at 23 weeks of gestational age. The proband had general appearance of Wolf-Hirschhorn syndrome and some unique findings, including single umbilical artery, severe immunoglobulin deficiency, scalp defect, and underlying bony defect. Our case underscores the importance of fetal karyotyping when low maternal serum free beta-HCG is found. It also adds information on the fetal presentations of monosomy 4p14-->pter and trisomy 11q25-->qter.

Prenatal diagnosis and molecular cytogenetic analysis of partial monosomy 10q (10q25.3→qter) and partial trisomy 18q (18q23→qter) in a fetus associated with cystic hygroma and ambiguous genitalia

OBJECTIVES

To present the prenatal diagnosis and molecular cytogenetic analysis of a fetus with nuchal cystic hygroma and ambiguous genitalia.

CASE AND METHODS

Amniocentesis was performed at 16 weeks' gestation because of the abnormal fetal sonographic finding of a large septated nuchal cystic hygroma. Genetic amniocentesis revealed a terminal deletion in the long arm of chromosome 10. The paternal karyotype was subsequently found to be 46,XY,t(10;18)(q25.3;q23). The maternal karyotype was normal. The pregnancy was terminated. A hydropic fetus was delivered with a septated nuchal cystic hygroma and ambiguous genitalia. Fluorescence in situ hybridization (FISH), microarray-based comparative genomic hybridization (CGH), and polymorphic DNA markers were used to investigate the involved chromosomal segments.

RESULTS

FISH study showed absence of the 10q telomeric probe and presence of the 18q telomeric probe in the derivative chromosome 10. Microarray-based CGH analysis showed loss of distal 10q and gain of distal 18q. Polymorphic DNA marker analysis determined the breakpoints. The fetal karyotype was 46,XY,der(10)t(10;18)(q25.3;q23)pat. The chromosome aberration resulted in partial monosomy 10q (10q25.3-->qter) and partial trisomy 18q (18q23-->qter).

CONCLUSIONS

The present case provides evidence that partial monosomy 10q (10q25.3-->qter) with partial trisomy 18q (18q23-->qter) can be a genetic cause of fetal cystic hygroma and ambiguous genitalia. Cytogenetic analysis for prenatally detected structural abnormalities may detect unexpected inherited chromosome aberrations.

Specificity of interphase fluorescence in situ hybridization for detection of chromosome aberrations in tumor pathology

Interphase fluorescence in situ hybridization (IFISH) is an interesting and intriguing cytogenetic approach in the study of tumor chromosomal abnormalities when metaphases are not available. This technique can be applied to different types of tumor nuclei, including imprinted nuclei (IM), nuclei obtained from conventional cytogenetic procedures (PB), frozen nuclei, paraffin-embedded nuclei (PE), and nuclei extracted from paraffin-embedded sections (EX). IFISH is a high-sensitivity approach in tumor studies that can give evidence of genetic aberrations present in a small percentage of cells that are likely to escape detection if only molecular techniques are applied. Despite its high sensitivity and versatility, IFISH is an indirect cytogenetic method and needs controls to have adequate specificity. This study includes present data obtained in IFISH experiments using different types of probes (alpha-satellite and YAC clones) hybridized on different types of normal control nuclei, such as PB, IM, EX, and PE nuclei, to define the threshold level for monosomy and trisomy of different chromosomal regions. My findings demonstrate that the cut-off values depend both on the types of probes and on the types of target nuclei. Therefore, even if IFISH is a versatile, high-sensitivity technique for detecting chromosomal abnormalities, the lack of accurate controls may result in the misdiagnosis of some abnormalities.

Del(18p) syndrome with increased nuchal translucency in prenatal diagnosis

We report a de novo translocation between chromosome 15 and 18 resulting in monosomy 18p in prenatal diagnosis. The patient was referred for amniocentesis due to increased nuchal translucency (INT) (5 mm) at 13.6 weeks of gestation. Karyotype of the fetus revealed 45,XX,der(15;18)(q10;q10) in all metaphases. The targeted fetal ultrasound at 20 weeks of gestation did not show any special physical abnormalities other than 6.4 mm of nuchal fold thickness. Molecular cytogenetic findings using CGH and FISH confirmed the del(18p) with dicentromeres from both chromosome 15 and 18. The present study shows that the INT at first trimester was the only prenatal finding for the fetus with del(18p) syndrome and that molecular cytogenetic methods are useful for detecting chromosomal aberrations precisely.

Genitourinary phenotype in XX patients with distal 9p monosomy

Although testicular development has been shown to be variably impaired in XY patients with distal 9p monosomy, ovarian and other genitourinary phenotype has poorly been studied in XX patients monosomic for the distal 9p region. Thus, we studied a 13-month-old infant with 46,XX,der(9)t(9;10)(p23;p13) (case 1) and an 11-year-old girl with 46,XX,der(9)t(9;16)(p23;q22) (case 2). Case 1 had primary hypogonadism (basal serum follicle stimulating hormone [FSH], 40.0 mIU/mL; leteinizing hormone [LH], 1.2 mIU/mL; estradiol [E2], <10 pg/mL), whereas case 2 had age-appropriate pubertal development (breast, Tanner stage 4; pubic hair, Tanner stage 3; menarche 11.7 years of age) and hormone values (FSH, 7.3 mIU/mL; LH, 6.7 mIU/mL; E2, 47 pg/mL). In addition, case 1 had hypoplastic labia majora, short distance between the vaginal orifice and the anus, and five renal cysts, and case 2 had anal atresia, short distance between the vaginal orifice and the anus, bilateral hydronephrosis of grade 3 with probable ureteropelvic junction stenosis, and renal dysfunction (serum creatinine, 1.52 mg/dL; urea nitrogen, 34.5mg/dL). Fluorescence in situ hybridization analysis for five regions and microsatellite analysis for 10 loci on 9p confirmed hemizygosity for the distal 9p region with the breakpoints between IFNA and D9S285 in case 1 and between D9S168 and D9S286 in case 2. The results, in conjunction with the previous data in XX patients with molecularly defined distal 9p monosomy, are consistent with the presence of a gene(s) involved in the development of indifferent gonad or subsequent ovarian differentiation in a approximately 11 Mb region distal to D9S168. In addition, it is possible that a gene(s) for anoperineal and renal development also maps distal to D9S168 and that for external genital development maps distal to D9S285 at the position approximately 16 Mb from the 9p telomere.

Redundant skin over the nape in a girl with monosomy 1p36 caused by a de-novo satellited derivative chromosome: a possible new feature?

We present a case of monosomy 1p36 who, in addition to delayed growth and development, and mild facial dysmorphism also had redundant skin over the nape. Chromosome analysis showed that the monosomy 1p36 was caused by a de-novo satellited derivative chromosome. We propose that the redundant skin over the nape should be considered as a feature of this condition.

Frequency of monosomy X in women with primary biliary cirrhosis

The mechanisms that cause the female predominance of primary biliary cirrhosis (PBC) are uncertain, but the X chromosome includes genes involved in immunological tolerance. We assessed the rate of X monosomy in peripheral white blood cells from 100 women with PBC, 50 with chronic hepatitis C, and 50 healthy controls, by fluorescence in-situ hybridisation. Frequency of X monosomy increased with age in all groups, but was significantly higher in women with PBC than in controls (p<0.0001); age-adjusted back-transformed mean frequencies were 0.050 (95% CI 0.046-0.055) in women with PBC, 0.032 (0.028-0.036) in those with chronic hepatitis C, and 0.028 (0.025-0.032) in controls. We suggest that haploinsufficiency for specific X-linked genes leads to female susceptibility to PBC.

Determination of cutoff values to detect small aneuploid clones by interphase fluorescence in situ hybridization: the Poisson model is a more appropriate approach. Should single-cell trisomy 8 be considered a clonal defect?

We applied a dual-color interphase in situ fluorescence hybridization (I-FISH) technique using centromeric probes specific to chromosomes 7 and 8 on 20 control samples in order to define the statistical model best suited to determine cutoff values for detection of small abnormal clones. We found that the Poisson model is a more appropriate approach than a Gaussian model. Then, based on the analysis of 91 samples from 80 patients with myelocytic malignant hemopathies and either clonal or nonclonal -7 or +8 as determined with conventional cytogenetics (CC), we compared the respective power of I-FISH and CC for detection of aneuploidy, with special emphasis on the potential contribution of I-FISH as a complement to CC in the case of small abnormal clones. The I-FISH results were positive in samples with clonal -7 or +8 according to CC analysis. Whereas I-FISH was negative in samples with nonclonal -7 according to CC, thus confirming the reliability of the criteria used to define the clonality of -7; the situation was different with nonclonal +8. I-FISH revealed the clonality of +8 in most samples with single-cell +8. In several cases, however, the unquestionable clonal nature of +8, as evidenced during follow-up, could not be established with either CC or I-FISH according to accepted criteria. Our data suggest that, in case of a single metaphase with +8, the general rule should be amended and the single-cell +8 should be considered and reported as potentially clonal.

A prenatally diagnosed patient with full monosomy 21: Ultrasound, cytogenetic, clinical, molecular, and necropsy findings

We report on a patient with a full monosomy 21 (FM21) prenatally diagnosed in cord fetal blood, and subsequently confirmed in other tissues. Subtle chromosomal translocations of chromosome 21, were ruled-out by FISH using both painting and 21q telomeric probes. Microsatellites analysis demonstrated the paternal origin of the single chromosome. The propositus showed at 32 weeks of gestation a severe intrauterine growth retardation and microcephaly. He was born with multiple congenital malformations, hypotonia, microcephaly, bilateral microphthalmia (more severe on the left), facial dysmorphism, agenesis of the external auditory meatus, redundant skin in the neck, narrow chest, flat scrotum, cryptorchydism, hypospadias, micropene, camptodactyly, nail hypoplasia, and abnormal palmar and plantar creases. The patient died in the first day of life. At necropsy, micrencephaly, semilobar holoprosencephaly, polimicrogyria, ocular abnormalities, skeletal anomalies, congenital heart disease, and agenesis of right kidney were also observed. To our best knowledge, this case is one of the most completely patient studied with FM21.

Monosomy 1p36 breakpoint junctions suggest pre-meiotic breakage-fusion-bridge cycles are involved in generating terminal deletions

Terminal deletions of 1p36 result in a mental retardation syndrome that is presumably caused by haploinsufficiency of a number of genes. Although monosomy 1p36 is the most commonly observed terminal deletion syndrome in humans, the molecular mechanism(s) that generates and stabilizes terminal deletions of 1p36 is not completely understood. Our previous molecular analysis of a large cohort of monosomy 1p36 subjects demonstrated that deletion sizes vary widely from approximately 1 Mb to >10.5 Mb in the most distal portion of 1p36 with no single common breakpoint. In this report, we have identified the precise breakpoint junctions in three subjects with apparently pure terminal deletions of 1p36 ranging from 2.5 to 4.25 Mb. These junctions revealed one deletion to be stabilized by telomeric repeat sequences and two to have terminal deletions associated with cryptic interrupted inverted duplications at the ends of the chromosomes. These interrupted inverted duplication/deletion breakpoints are reminiscent of those seen in tumor cell lines that have undergone breakage-fusion-bridge (BFB) cycles leading to gene amplification. We propose a pre-meiotic model for the formation of these deletions in which a terminally deleted chromosome is generated in the germ line and passes through at least one BFB cycle to produce gametes with terminal deletions associated with interrupted inverted duplications. These data suggest that, on a molecular level, seemingly pure terminal deletions visualized cytogenetically may be more complex, and BFB cycles may play an important role in generating terminal deletions associated with genetic disease in humans.

Physical map of 1p36, placement of breakpoints in monosomy 1p36, and clinical characterization of the syndrome

Monosomy 1p36 is the most common terminal deletion syndrome. This contiguous gene deletion syndrome is presumably caused by haploinsufficiency of a number of genes. We have constructed a contig of overlapping large-insert clones for the most distal 10.5 Mb of 1p36, evaluated the deletion sizes in 61 subjects with monosomy 1p36 from 60 families, and created a natural deletion panel. We found pure terminal deletions, interstitial deletions, derivative chromosomes, and more complex rearrangements. Breakpoints were "binned" into 0.5-Mb regions. Analyses revealed some clustering of breakpoints but no single common breakpoint. Determination of the parental origin showed that 60% of de novo 1p36 terminal deletions arose from the maternally inherited chromosome. Of the 61 subjects, 30 were examined systematically through a protocol at the Texas Children's Hospital General Clinical Research Center. Specifically, we report hearing evaluations, palatal and ophthalmological examinations, echocardiograms, neurological assessments, and thyroid function tests. To our knowledge, this systematic molecular and clinical characterization of monosomy 1p36 is the largest and most comprehensive study of this deletion syndrome to date. Many cytogenetically visible, apparent terminal deletions are more complex than anticipated by cytogenetics, as revealed at the molecular level by our study. Our clinical findings allow for the more accurate recognition of the syndrome and for proper medical evaluation.

[Detection of trisomy 8 and monosomy 7 in chronic granulocytic leukemia and myelodysplastic syndrome by cytogenetic analysis and fluorescence in situ hybridization]

INTRODUCTION AND AIMS

In this retrospective study the authors studied how interphase fluorescence in situ hybridization can be applied to the diagnosis of numerical chromosomal anomalies failed to be identified by cytogenetic analysis.

METHODS

Thirty-four patients, 27 with chronic granulocytic leukemia and seven with myelodysplastic syndrome, were studied in order to identify disease-specific aberrations, trisomy 8 and monosomy 7 using both traditional cytogenetic analysis and fluorescence in situ hybridization on interphase bone marrow cells. Using alphoid-satellite centromeric specific probes, trisomy 8 indicating the progression of the disease and poor prognosis in chronic granulocytic leukemia as well as monosomy 7 in myelodysplastic syndrome were identified.

RESULTS

In 21 of 34 cases both methods led to the same results. In 13 patients fluorescence in situ hybridization making possible to examine a great number of cells, provided more information about the gain and loss of chromosomes above and clarified uncertain cytogenetic results.

CONCLUSIONS

In both hematological malignancies, studied by the authors, fluorescence in situ hybridization proved a useful and sensitive method to determine chromosomes unrecognized or not accurately identified by the traditional cytogenetic analysis and to define the ratio of pathological cells. At the same time the results confirm that conventional cytogenetic analysis is still essential in diagnosing the genetic alterations of malignant cells and point at the chromosomes that are worth further studying by other methods.

Loss of chromosome 16 from renal epithelial cells in humans

This work explores the notion that low-frequency, acquired aneuploidy may play a role in complex genetic traits such as essential hypertension. To this end, renal epithelial cells in urinary sediments and in renal cysts were examined by fluorescent in situ hybridization with DNA probes specific for the heterochromatic and centromere regions of chromosomes 16 and 1. Chromosome 16 was probed because it harbors variant genes causing monogenic hypertension. These genes have also been investigated for their role in essential hypertension. Chromosome 1 was also probed as an internal control. Higher proportions of renal epithelial cells in the urinary sediments showed monosomy of chromosome 16 than monosomy of chromosome 1 (P<0.001). We also observed in epithelial cells of renal cysts a preponderance of monosomy for chromosome 16 over monosomy for chromosome 1 (P<0.024). Low-frequency loss of heterozygosity that results from acquired monosomy of chromosome 16 and perhaps other chromosomes may contribute to expression of complex genetic traits such as essential hypertension, in which the diverse phenotypic manifestations are poorly understood.

Cardiac malformations in first-trimester fetuses with increased nuchal translucency: ultrasound diagnosis and postmortem morphology

OBJECTIVE

The aim of this study was to explore the diagnostic accuracy of first-trimester transvaginal echocardiography in fetuses with increased nuchal translucency (NT) thickness, by comparing the ultrasound diagnosis with the findings on postmortem examination or mid-gestational ultrasound and neonatal outcome.

METHODS

Transvaginal echocardiography was performed in 45 fetuses with a NT > 95th centile. Karyotyping was performed in 43. In 20 of the 23 pregnancies in which termination of pregnancy was carried out, postmortem examination was performed to determine the presence and type of heart defect. Mid-gestational echocardiography was performed in ongoing pregnancies and neonatal follow-up information was obtained. Findings on first-trimester transvaginal echocardiography were compared to those of second-trimester echocardiography or the results of postmortem examination. The mean NT in the fetuses with and without heart defects was calculated.

RESULTS

Of the 45 fetuses, heart malformations were suspected on first-trimester ultrasound in 10 (22%), of which eight (80%) were found to have a chromosomal abnormality. Postmortem examination showed minor additional findings in some cases and major discrepancies occurred in none. Septal defects were the most common defects in trisomic fetuses. In three fetuses with a 45 X karyotype, hypoplastic left heart syndrome was diagnosed. Heart defects were diagnosed in three euploid fetuses in which fetal demise occurred. The sensitivity and specificity for the detection of heart defects of transvaginal echocardiography were 88% and 97%, respectively. The mean NT in fetuses with a normal heart (4.3 mm) was significantly smaller than that of fetuses with heart defects (7.4 mm).

CONCLUSION

Transvaginal echocardiography can be performed reliably in first-trimester fetuses with an increased NT. In this study, the proportion of chromosomally abnormal fetuses with a heart defect was not different from that found in newborns, except for cases of Turner syndrome. Fetal demise occurred in all three euploid fetuses with a heart malformation. The fetuses with a heart defect had a larger NT than did those without.

Complete karyotype discrepancy between placental and fetal cells in a case of ring chromosome 18

A case of complete karyotype discrepancy between cultured chorionic villi and amniotic in addition to fetal cells is reported. Ring chromosome 18 and monosomy 18 mosaicism was detected after amniocentesis. The pregnancy was terminated in the 23rd gestational week. Cytogenetic analysis of cultured umbilical cord tissue after termination confirmed the finding of ring chromosome 18/monosomy 18 mosaicism. In cultured umbilical blood lymphocytes monosomic cells 45,-18 were not detected and the karyotype was 46,XY,r(18). In contrast, short-term and long-term cultured chorionic villi showed a normal male karyotype of 46,XY. Ultrasonographic examination revealed amniotic band syndrome and scoliosis in the caudal region of the spine.

The role of comparative genomic hybridisation in prenatal diagnosis

The aims of this study were to assess the feasibility of using comparative genomic hybridisation instead of conventional cytogenetics in prenatal diagnosis and to determine the size of DNA loss that can be detected. Using comparative genomic hybridisation, six cases with standard aneuploidies were diagnosed correctly. This technique clearly identified a partial duplication of the long arm of chromosome 1 but was not capable of detecting the associated inversion. A small interstitial deletion on short arm of chromosome 10 also was detected precisely. Although the current comparative genomic hybridisation resolution is similar to the sensitivity of the highest resolution G banding, the latter is not a routine strategy in prenatal diagnosis. Comparative genomic hybridisation can allow full chromosome assessment equal to the highest resolution cytogenetic studies without the need for cell culture.

Masked monosomy 7 in myelodysplastic syndromes is uncommon and of undetermined clinical significance

Masked monosomy 7, i.e. detected by FISH but not by conventional cytogenetics, has been reported in varying frequency in MDS. To establish the prevalence and possible clinical significance of the aberration, we studied the 123 previously karyotyped MDS patients using FISH and a DNA probe specific for chromosome 7. Metaphase cytogenetics revealed ten patients (8%) with monosomy 7 (6 RAEB and 4 RAEB-t). FISH confirmed this result and detected four more cases (4%) with masked monosomy 7 (3 RA and 1 RARS). Thus, masked monosomy 7 is less common than has been suggested, and does not seem to carry the same prognostic weight as monosomy 7 diagnosed by metaphase cytogenetics.