An unusual three-way translocation t(21;8;1)(q22;q22;q32) in a case of acute myeloid leukemia (M2).

Variant forms of the classic translocation t(8;21) are uncommon and account approximately 3% of all t(8;21)(q22;q22) in acute myeloid leukemia (AML) patients. These forms involve chromosomes 8, 21, and other chromosomes. Here we report a Tunisian patient with a complex rearrangement t(21;8;1)(q22;q22;q32) revealed by conventional chromosomal study at diagnosis. Fluorescence in situ hybridization study revealed the presence of the AML1-ETO chimeric gene on the derivative chromosome 8. To the best of our knowledge, this is the second case of t(21;8;1) of AML-M2 reported in the literature with the involvement of the same breakpoint at 1q32. This illustrates that this complex translocation is rarely encountered in AML and reinforces the fact that this region may harbour a critical gene candidate that may play an important role in the pathogenesis of AML. More cases are needed to elucidate its clinical features and prognosis.

Array-CGH study of partial trisomy 9p without mental retardation.

Partial trisomy 9p is one of the most common detected autosomal structural anomalies, so the phenotype-genotype correlation of this rearrangement has been well described. Despite variation in size of the 9p duplications, trisomy 9p syndrome is characterized by typical dysmorphic features and a variable but constant psychomotor and mental retardation. Previously reported phenotype genotype correlation studies proposed that the critical region for phenotype is located in 9p22. We report here on a new patient with partial trisomy 9p13.3→9pter in an 8-year-old boy with typical trisomy 9p dysmorphic features but a normal mental development. Cytogenetics investigations showed that our patient karyotype was 47,XY,+ der(22)t(9;22)(p13.q11) inherited by a 3:1 disjunction of a maternal reciprocal translocation t(9;22)(p13.q11). FISH and array CGH analysis were used to better characterize duplicated chromosomal regions and showed a large duplication of chromosome 9p13.3→9pter associated to microduplication in 22q11.1. The size of the duplications in chromosomes 9p and 22q were estimated about 33.9 and 2.67 Mb, respectively. The comparison between this case and those reported in the literature allows us to support that all syndromes show variability and that not all partial trisomies 9p are associated with intellectual disability.

Cytogenetic abnormalities in Tunisian de novo myelodysplastic syndrome: a comparison with other populations.

Cytogenetic analysis was performed on 224 bone marrow (BM) of Tunisian patients with de novo myelodysplastic syndrome (MDS) at our institution from January 1993 to December 2006. According to French-American-British (FAB) criteria, there were 36% of patients with refractory anaemia (RA), 26% with refractory anaemia with excess of blasts (RAEB), 10% with refractory anaemia with ringed sideroblasts (RARS), 12% with chronic myelomonocytic leukaemia (CMML), 9% refractory anaemia with excess of blasts in transformation (RAEB-t) and 7% of unclassified MDS. A clonal chromosomal abnormality was observed in 51% of the patients. The most frequent karyotypic change was 5q- in 30 cases (13%), followed by -7/7q- in 17 cases (8%), del(12p) in 8 cases (4%), del(20q) and trisomy 8 in 7 cases each (3%), i(17q) in 2 cases (1%) and -y in only one case (0.4%). This is the first large comparative series of MDS from an Arab country, with cytogenetic analysis showing haematological and cytogenetic features similar to those of MDS population of European or mixed European-subsaharian African origin (like Brazil), but different from those seen in Eastern populations.

Molecular cytogenetic and phenotypic characterization of ring chromosome 13 in three unrelated patients.

We report on the cytogenetic and molecular investigations of constitutional de-novo ring chromosome 13s in three unrelated patients for better understanding and delineation of the phenotypic variability characterizing this genomic rearrangement. The patient's karyotypes were as follows: 46,XY,r(13)(p11q34) dn for patients 1 and 2 and 46,XY,r(13)(p11q14) dn for patient 3, as a result of the deletion in the telomeric regions of chromosome 13. The patients were, therefore, monosomic for the segment 13q34 → 13qter; in addition, for patient 3, the deletion was larger, encompassing the segment 13q14 → 13qter. Fluorescence in situ hybridization confirmed these rearrangement and array CGH technique showed the loss of at least 2.9 Mb on the short arm and 4.7 Mb on the long arm of the chromosome 13 in patient 2. Ring chromosome 13 (r(13)) is associated with several phenotypic features like intellectual disability, marked short stature, brain and heart defects, microcephaly and genital malformations in males, including undescended testes and hypospadias. However, the hearing loss and speech delay that were found in our three patients have rarely been reported with ring chromosome 13. Although little is known about its etiology, there is interesting evidence for a genetic cause for the ring chromosome 13. We thus performed a genotype-phenotype correlation analysis to ascertain the contribution of ring chromosome 13 to the clinical features of our three cases.

Multiple myeloma following essential thrombocythemia.

The association of essential thrombocythemia and multiple myeloma is extremely rare, with only three patients previously treated with hydroxyurea reported in the literature until now. In this paper, we report the case of a 66 year old male who developed IgG-kappa M six years after the diagnosis of essential thrombocythemia, for which he had received hydroyurea. The possible etiological and pathogenic link between both these entities is here discussed.

Trisomy and tetrasomy 15q11-q13 diagnosed by molecular cytogenetic analysis in two patients with mental retardation.

In this study, we report two patients with the supernumerary marker chromosome (15)s. The first case is an 8.5-year-old girl with an inv dup (15) syndrome, mental retardation and dysmorphic features. The second case is a 13-year-old boy with a ring chromosome 15, who was referred to the Laboratory of Cytogenetic and Biology of Reproduction in Sousse, Tunisia for mental retardation, epilepsy, speech delay, hypotonia and other mild dysmorphic features. R banding showed the presence of a marker chromosome in both cases. Molecular cytogenetic investigation using fluorescence in situ hybridization method allowed us to characterize the markers including the Prader-Willi syndrome locus that contains the small nuclear ribonucleoprotein polypeptide N (SNRPN) gene. Tetrasomy and trisomy for the 15q11-q13 chromosomal region were found in the first and the second patient, respectively. This observation reinforces the hypothesis that additional copies of proximal chromosome 15q11 segment may be causally related to mental retardation and dysmorphic features.

Cytogenetic analysis in a large series of children with non-syndromic mental retardation.

Mental retardation affects 1-3% of the population. To evaluate the implication of chromosomal abnormalities in the etiology of mental retardation, 1420 patients with non-syndromic mental retardation recruited at the department of cytogenetics of Farhat Hached hospital (Sousse, Tunisia) between January 2005 and December 2009, were analyzed using standard cytogenetic techniques. Age ranged between 3 and 18 years with a median of 8 years. Chromosomal abnormalities were detected in 7.8% of patients and an increased prevalence of chromosome anomalies was observed in patients when the mental retardation is associated with a severe degree of intellectual disability, facial dysmorphic features and/or congenital malformations or epilepsy.

Chromosomal microarray analysis of functional Xq27-qter disomy and deletion 3p26.3 in a boy with Prader-Willi like features and hypotonia.

Duplications of the long arm of the X chromosome are rare. The infantile phenotype shares some resemblance with the Prader-Willi syndrome, presenting severe psychomotor retardation, facial dysmorphic features with a broad face, a small mouth and a thin pointed nose, hypotonia, urogenital malformation and proneness to infections. We report a boy with an additional Xq27-qter chromosome segment translocated onto the short arm of chromosome 3. The karyotype was 46,XY,der(3)t(X;3)(q27.3; p26.3)mat. This cryptic unbalanced X-autosome translocation resulted in Xq27-qter functional disomy and a deletion 3p26.3. A detailed analysis of the constitutional chromosomal changes in the patient was performed using array-CGH, FISH and PCR. The aim was to characterize the size and the location of the duplication Xq27-qter (8.18 Mb) and of the deletion 3p26.3 (1.05 Mb), to establish phenotype-genotype correlations and to offer genetic counselling.

Cytogenetic profile of a large cohort of Tunisian de novo acute myeloid leukemia.

BACKGROUND: Cytogenetic data are essential not only for the diagnosis of acute myeloid leukemia but also for the evaluation of prognosis. Large systematic studies of cytogenetic aberrations in patients with acute myeloid leukaemia (AML) from Arab countries are not available. METHODS: We analysed 631 consecutive newly diagnosed AML patients by conventional cytogenetics and compared our results with reports from other regions of the world. There were 97 (15·4%) children and 534 (84·6%) adults. RESULTS: Abnormal karyotypes were found in 397 (62·9%) of all cases. T(15;17) and t(8;21) were the most frequent chromosomal abnormalities observed in 83 (13·2%) and in 78 (12·4%) patients, respectively. -5/del(5q) and -7/del(7q) were less frequent, seen in only 14 (2·2%) and 19 (3%) cases, respectively. Trisomy 8 was found in 44 (7%) of our patients followed by 11q23 rearrangements seen in 24 (3·8%) and then by inv(16) observed in only 22 (3·5%) of all cases. Unusual or novel cytogenetic abnormalities were found in 107 (17%) of our patients. DISCUSSION: Although we confirmed, as usually described, that some recurrent cytogenetic abnormalities are correlated with the FAB subtypes, we noted however that some of them vary in frequency among different geographical areas and ethnic groups. This finding suggests a geographic heterogeneity in the pathogenesis of AML but more extensive epidemiological studies are required to confirm this.

T(1;21;8)(p34;q22;q22): a novel variant of t(8;21) in acute myeloblastic leukemia with maturation.

The complex variants of t(8;21) involving chromosomes 8 and 21 as well as another chromosome account for approximately 3% of acute myeloid leukemia patients. We report here a 30-year-old male patient with AML-M2. Fluorescence in situ hybridization analysis using dual-color fluorescence ETO and AML1 probes located at 8q22 and 21q22 respectively showed an AML1/ETO fusion signal on the derivative chromosome 8. Whole chromosome painting probes were used for chromosome 1, 8 and 21 and revealed a three-way translocation (1;21;8)(p34 ~ p35;q22;q22). Involvement of chromosome region 1p34 has never been reported earlier, although region 1p35 as a variant in AML with t(8;21) has been reported with an AML1/ETO fusion signal on the 1p35 rather than der(8). In conclusion, combining conventional karyotype, FISH or RT-PCR analyses are a rational strategy for the identification of the complex variants of t(8;21) translocation which could be critical events responsible for leukemogenesis.

ETV6-RUNX1 Rearrangement in Tunisian Pediatric B-Lineage Acute Lymphoblastic Leukemia.

In this study, Forty-one out of fifty-seven Tunisian children with B-lineage acute lymphoblastic leukemia (B-ALL), and without cytogenetically detectable recurrent abnormalities at the time of the diagnosis, were evaluated by fluorescence in situ hybridization (FISH) for the t(12;21). This translocation leads ETV6-RUNX1 (previously TEL-AML1) fusion gene. 16 patients (28%) had ETV6-RUNX1 rearrangement. In addition to this rearrangement, two cases showed a loss of the normal ETV6 allele, and three others showed an extra signal of the RUNX1 gene. Seven patients without ETV6-RUNX1 rearrangement showed extra signals of the RUNX1 gene. One out of the 7 patients was also associated with a t(3;12) identified by FISH. This is the first Tunisian study in which we report the incidence of t(12;21) among childhood B-lineage ALL and in which we have found multiple copies of RUNX1. Finally, our findings confirm that additional or secondary genetic changes are commonly encountered in pediatric B-lineage ALL with ETV6-RUNX1 gene fusion which is envisaged to play a pivotal role in disease progression.

Cytogenetic analysis of 298 newly diagnosed cases of acute lymphoblastic leukaemia in Tunisia.

Genetic changes associated with Acute Lymphoblastic Leukaemia (ALL) provide diagnostic and prognostic information with a direct impact on patient management. We report the cytogenetic analysis of 298 Tunisian patients with ALL, including 183 children and 115 adults. Chromosome abnormalities have been detected in 68.2% of our patients associating clonal numerical and/or structural rearrangements. Some chromosomal abnormalities especially hyperdiploidy, 19p13 abnormalities, 8q24 translocations, 12p, 6q deletions and TCR rearrangements occur at a lower incidence compared to that reported in other populations. ALL cases (5.7%) had miscellaneous clonal abnormalities. We also found in our Tunisian series a higher incidence for T-lineage ALL more than usually described. Among structural chromosomal abnormalities, t(9;22)(q34;q11) resulting in the BCR/ABL fusion and the t(12;21)(p13;q22) resulting in the TEL/AML1 fusion were studied by FISH providing additional diagnostic and prognostic information. We conclude that although the incidence of our cytogenetic results are slightly different, their clinical significance is similar to that described in the literature.