Search for deletion 22q11.2 in interphase nuclei of buccal mucosa of patients ascertained by isolated cleft palate: a new diagnostic approach

The 22q11.2 Microdeletion in Pediatric Patients with Cleft Lip, Palate, or Both and Congenital Heart Disease: A Systematic Review

The 22q11.2 deletion syndrome (22q11.2DS) is present in approximately 5 to 8% of patients with cleft lip, palate, or both (CL/P) and 75 to 80% of patients with congenital heart disease (CHD). In a literature review, we consider this association of 22q11.2DS in pediatric patients with CL/P and CHD. Early diagnosis of 22q11.2DS in pediatric patients with CL/P and CHD helps to optimize a multidisciplinary treatment approach for 22q11DS. Early diagnosis, thereby, can improve quality of life for these patients and awareness of other potential clinical implications that may require attention throughout the patient's life.

Clinical Correlation of Chromosome 22q11.2 Fluorescent in Situ Hybridization Analysis and Velocardiofacial Syndrome

Objective:

To identify characteristics associated with microdeletions of chromosome 22q11.2 ascertained by fluorescent in situ hybridization (FISH) analysis in patients with velopharyngeal insufficiency (VPI), cleft palate, or other clinical features of velocardiofacial syndrome (VCFS).

Design/Setting:

Retrospective review of all patients entered at one tertiary-level multidisciplinary cleft lip and palate and craniofacial anomalies panel from January 2000 to December 2003.

Patients:

The study consisted of 115 patients. The presence or absence of the following clinical features was documented: cleft palate (submucous and overt), VPI, cardiac anomalies, renal anomalies, small stature, characteristic facies, developmental delay, psychiatric dysfunction, and family history.

Main Outcome Measure:

Correlation between presence or absence of clinical features of VCFS and presence or absence of 22q11.2 microdeletion by FISH analysis.

Results:

Of the 16 patients (13.9%) who demonstrated 22q11.2 microdeletion by FISH analysis, 16 had VPI (100%), 16 had small stature (100%), 14 had cleft palate (88%), and 13 had characteristic facies (81%). Developmental delay was also present in 13 of these patients (81%), and seven had cardiac anomalies (44%). Multiple regression analysis revealed that the presence of characteristic facies and small stature statistically correlated with microdeletions of chromosome 22q11.2 by FISH studies (p < .05).

Conclusions:

Patients with microdeletions of chromosome 22q11.2 as demonstrated by FISH analysis were more likely to have VPI, small stature, cleft palate, characteristic facies, and developmental delay, in descending order. Statistical analysis showed that only characteristic facies and small stature correlated with 22q11.2 microdeletions.

The use of fluorescence in situ hybridization in the diagnosis of hidden mosaicism: apropos of three cases of sex chromosome anomalies

FISH has been used as a complement to classical cytogenetics in the detection of mosaicism in sex chromosome anomalies. The aim of this study is to describe three cases in which the final diagnosis could only be achieved by FISH. Case 1 was an 8-year-old 46,XY girl with normal female genitalia referred to our service because of short stature. FISH analysis of lymphocytes with probes for the X and Y centromeres identified a 45,X/46,X,idic(Y) constitution, and established the diagnosis of Turner syndrome. Case 2 was a 21-month-old 46,XY boy with genital ambiguity (penile hypospadias, right testis, and left streak gonad). FISH analysis of lymphocytes and buccal smear identified a 45,X/46,XY karyotype, leading to diagnosis of mixed gonadal dysgenesis. Case 3 was a 47,XYY 19-year-old boy with delayed neuromotor development, learning disabilities, psychological problems, tall stature, small testes, elevated gonadotropins, and azoospermia. FISH analysis of lymphocytes and buccal smear identified a 47,XYY/48,XXYY constitution. Cases 1 and 2 illustrate the phenotypic variability of the 45,X/46,XY mosaicism, and the importance of detection of the 45,X cell line for proper management and follow-up. In case 3, abnormal gonadal function could be explained by the 48,XXYY cell line. The use of FISH in clinical practice is particularly relevant when classical cytogenetic analysis yields normal or uncertain results in patients with features of sex chromosome aneuploidy.

Genetic compensation in a human genomic disorder

Cytogenetic studies of the parents of a girl with the DiGeorge (or velocardiofacial) syndrome, who carried a deletion at 22q11.2, revealed an unexpected rearrangement of both 22q11.2 regions in the unaffected father. He carried a 22q11.2 deletion on one copy of chromosome 22 and a reciprocal 22q11.2 duplication on the other copy of chromosome 22. Genetic compensation, which is consistent with the normal phenotype of the father, was shown through quantitative-expression analyses of genes located within the genetic region associated with the DiGeorge syndrome. This finding has implications for genetic counseling and represents a case of genetic compensation in a human genomic disorder.

22q11 chromosome abnormalities and the cleft service

Deletion of chromosome 22q11 gives rise to a spectrum of anomalies, including cleft palate. These are grouped together as the DiGeorge or velocardiofacial syndrome. Patients with this chromosomal abnormality account for a small, but noteworthy proportion of patients attending our cleft service. They frequently have other significant comorbidities consistent with their diagnosis. Over a ten-year period, 16 patients within our cleft service have been diagnosed, using chromosome analysis, as having deletions at 22q11. All had either a cleft palate and/or velopharyngeal incompetence, for which they underwent repair of the cleft palate or pharyngoplasty. Several have required secondary palate surgery following initial palate surgery. Poor quality of speech was the indication for secondary procedures in the majority of cases. Fourteen of the 16 have other comorbidities, ranging from congenital heart disease to ocular abnormalities. In addition, 15 of the 16 have developmental delays and/or learning difficulties. Other specialties, such as ENT, cardiology, genetics and ophthalmology have been involved in the care of all these patients. Although comprising only a small proportion of patients attending a cleft team, the diagnosis of this chromosomal abnormality is significant, as these patients may require substantial input of resources and the expertise of several specialties. Early recognition of features of this entity and diagnosis can aid more efficient intervention.

A novel t(8;18)(q13;q21) in acute monocytic leukemia evolving from constitutional trisomy 8 mosaicism

Constitutional trisomy 8 mosaicism (CT8M) has been considered to be the first mutation in multistep carcinogenesis. We describe the case of a 38-year-old woman with a normal phenotype who developed to acute monocytic leukemia with a novel t(8;18)(q13;q21). Chromosome analysis and spectral karyotyping showed 47,XX,+8,t(8;18)(q13;q21)[20]. Fluorescence in situ hybridization (FISH) demonstrated that the breakpoint at 18q21 was centromeric to the MALT1 and BCL2 genes. FISH also revealed that trisomy 8 was detected in buccal mucosa cells, indicating that trisomy 8 was a constitutional abnormality. These results suggest that t(8;18)(q13;q21) had a crucial role in the development of leukemia as the second mutation following CT8M.