Fluorescence in situ hybridization ( FISH ) screening for the 22 q 11 . 2 deletion in patients with clinical features of velocardiofacial syndrome but without cardiac anomalies

The velocardiofacial syndrome (VCFS), a condition associated with 22q11.2 deletions, is characterized by a typical facies, palatal anomalies, learning disabilities, behavioral disturbances and cardiac defects. We investigated the frequency of these chromosomal deletions in 16 individuals with VCFS features who presented no cardiac anomalies, one of the main characteristics of VCFS. Fluorescent in situ hybridization (FISH) with the N25 (D22S75; 22q11.2) probe revealed deletions in ten individuals (62%). Therefore, even in the absence of cardiac anomalies testing for the 22q11.2 microdeletions in individuals showing other clinical features of this syndrome is recommended.

Velocardiofacial syndrome (VCFS) is characterized by a complex of clinical anomalies: typical facies, velopharyngeal insufficiency (VPI) or cleft palate, learning disabilities, behavioral disturbances and cardiac anomalies (Shprintzen, 1990;Lipson et al., 1991).The typical facies includes a prominent nose with squared nasal root and narrow alar base, relative deficiency of the malar area, vertical maxillary excess, retruded mandible, narrow palpebral fissures and minor ear anomalies.Palatal anomalies, learning disabilities and typical facies are present in all patients.
Cardiac defects are found in 84% of the patients and are the main cause of morbidity and mortality (Shprintzen et al., 1981).Other less frequent features are psychiatric disorders, short stature and hyperextensibility of the digits.The estimated incidence of the syndrome is 1:4000 live births (Devriendt et al., 1998).
Cytogenetic studies using high-resolution chromosome banding have detected 22q11.2 deletions in approximately 20% of individuals with VCFS (Driscoll et al., 1992), whereas fluorescent in situ hybridization (FISH) analysis has demonstrated 22q11.2microdeletions in the majority of these patients (Lindsay et al., 1995 a,b).A clear correlation between the extension of the deletions and the clinical variability has not become evident (Carlson et al., 1997 a,b;Edelman et al. 1999;Digilio et al., 2003).
Some studies investigated the frequency of cardiac anomalies among carriers of 22q11.2deletions.In a European collaborative study of 558 individuals with 22q11 deletions (Ryan et al., 1997), 70% of the 545 individuals evaluated for cardiac anomalies had a significant cardiac pathology, such as Fallot's tetralogy, ventricular septal defect, interrupted aortic arch, pulmonary atresia/ventricular septal defect or truncus arteriosus.Similar frequencies were observed by McDonald-McGinn et al. (1999) and Kitsiou-Tzeli et al. (2004).However, Bassett et al. (2005) reported cardiac anomalies in 25.8% of 78 adults carrying 22q11 deletions.
To investigate the association of 22q11.2deletions with cardiac anomalies, we searched for 22q11.2deletions in individuals with clinical features of VCFS who did not present with cardiac anomalies.
After the approval by the Committee of Ethics in Research of the Ribeirão Preto Medical School University of São Paulo and obtaining written informed consent from the individuals or their legal guardians, we selected a group of 16 individuals (6 females, 10 males) among those referred to the Hospital de Pesquisa e Reabilitação de Lesões Lábio Palatais/USP (HPRLLP/Centrinho, Bauru, SP) with the diagnostic hypothesis of VCFS.These individuals were selected based on the main characteristics of the VCFS, i.e., typical facies, velopharyngeal insufficiency, behavioral disorders and/or learning disabilities.All of them were sporadic cases.
The 16 individuals with VCFS were submitted to a study protocol including standard semiology and family history, clinical, phonoaudiological and radiological exams.Learning disabilities, behavioral disturbances and mental retardation were assessed by psychological tests.Cardiac evaluation, including electrocardiogram and echodopplercardiogram, was carried out on all 16 individuals examined and those with cardiac alterations excluded from our study.The mean age of the group ranged from 6 to 32 years with a mean of 14 ± 5.9 years.Table 1 summarizes the clinical findings in our group.
The critical VCFS region (DGCR) encompasses about 3 Mb, which is deleted in about 90% of individuals with VCFS (Morrow et al., 1995).In addition to the 3 Mb deletion, another 8% of cases have been found to present a smaller deletion of about 1.5 Mb (Carlson et al., 1997a), and it has also been shown that in familial cases these smaller deletions were predominant (Adeyinka et al., 2004).The probe we used covered ~90 kb of the critical region and detected the majority of deletions.Nevertheless, the presence of deletions, which did not involve this segment, cannot be ruled out in our non-deletion individuals.
All our patients presented the characteristic clinical features of VCFS except for cardiac anomalies and, apart from this, there were no significant clinical difference between individuals with or without the 22q11.2deletion, agreeing with previously reported data (Lindsay et al., 1995a, Digilio et al 2003).
Frequencies of individuals without cardiac anomalies ranging from 25 to 70% have previously been reported among carriers of 22q11.2deletions (Ryan et al 1997;Mc-Donald-McGinn, 1999;Kitsiou-Tzeli et al., 2004;Bassett et al., 2005).To our knowledge this is the first study that determined the frequency of deletions in individuals with VCFS who had been selected on the basis of the absence of cardiac defects, and revealed the relatively high frequency of 62% deletions.
Testing for the presence of the 22q11.2deletion is recommended for patients with two or more relevant clinical features of VCFS in any combination (typical facies, cardiac anomalies, palatal anomalies and learning disabilities), particularly when the typical facies is associated with palatal anomalies (Scambler, 2000).The high frequency of 22q11.2deletion found in our small series of 16 individuals with VCFS without cardiac defects indicate that testing for deletions is recommended in such individuals.

Table 1 -
Clinical findings present in individuals with velocardiofacial syndrome (VCFS) but without cardiac anomalies.