22q11.2 deletion syndrome and complex congenital heart defects

Rosa, Rafael Fabiano Machado; Trevisan, Patrícia; Koshiyama, Dayane Bohn; Pilla, Carlo Benatti; Zen, Paulo Ricardo Gazzola; Varella-Garcia, Marileila; Paskulin, Giorgio Adriano

doi:10.1590/S0104-42302011000100018

Abstracts

OBJECTIVE: Investigate the frequency of 22q11 deletion syndrome among patients with complex congenital heart disease. METHODS: A prospective and consecutive cohort of patients with complex heart defects was evaluated in their first hospitalization at a cardiac intensive care unit of a pediatric hospital. For each patient a protocol of demographic and clinical evaluation was filled. High resolution karyotype and 22q11 microdeletion by fluorescence in situ hybridization was investigated. The heart defects were classified by a cardiologist of the study. RESULTS: The cohort comprised 66 patients. Karyotypic anomalies were observed in 5 patients (7.6%), however none of those was the 22q11 deletion. Evaluation by means of FISH was successful in 65 patients and 22q11 microdeletion was identified in 2 (3.1%). Of the 66 patients with complex defects, 52 were carriers of conotruncal malformations and in 51 the 22q11 microdeletion analysis by FISH was successful. Both 22q11 microdeletion carriers belonged to this group, representing a frequency of 3.9%. They presented tetralogy of Fallot. CONCLUSION: 22q11DS is a frequent abnormality among patients with complex and conotruncal heart defects. Variations of the 22q11DS frequency among studies seem to be mainly associated to criteria for patient selection and specific characteristics of the population in analysis.

DiGeorge syndrome; in situ hybridization; fluorescence; heart defects; congenital; chromosomes, human, pair 22

OBJETIVO: Verificar a frequência da síndrome de deleção 22q11 (SD22q11) entre pacientes portadores de cardiopatia congênita do tipo complexa. MÉTODOS: A amostra foi constituída por uma coorte prospectiva e consecutiva de pacientes com cardiopatia complexa em sua primeira hospitalização em uma unidade de tratamento intensivo cardiológica de um hospital pediátrico. Para cada paciente foi preenchida uma ficha de avaliação, com coleta de dados clínicos, e realizado o cariótipo de alta resolução e técnica de hibridização in situ fluorescente (FISH) com pesquisa de microdeleção 22q11. Os defeitos cardíacos foram classificados por um cardiologista participante do estudo. RESULTADOS: A amostra foi composta de 66 pacientes. Quanto à análise cariotípica, alterações foram observadas em cinco pacientes (7,6%); contudo, nenhum deles apresentava deleção 22q11. A avaliação pela técnica de FISH pôde ser realizada com sucesso em 65 pacientes, sendo que a microdeleção 22q11 foi identificada em dois (3,1%). Dos 66 pacientes com defeitos complexos, 52 eram portadores de malformações do tipo conotruncal, sendo que em 51 a pesquisa para microdeleção 22q11 foi realizada. Os dois pacientes portadores da microdeleção 22q11 fizeram parte deste grupo, representando uma frequência de 3,9%. Eles apresentavam tetralogia de Fallot. CONCLUSÃO: A SD22q11 é uma anormalidade frequente entre pacientes com cardiopatias congênitas complexas e conotruncais. Variações da frequência da SD22q11 entre os estudos parecem estar associadas, principalmente, com a forma adotada para a seleção da amostra e às características da população em análise.

Síndrome de DiGeorge; hibridização in situ fluorescente; cardiopatias congênitas; cromossomos humanos par 22

ORIGINAL ARTICLE

^IM. Sc.; PhD student in Pathology at Universidade Federal de Ciências da Saúde de Porto Alegre - UFCSPA, Porto Alegre, RS, Brazil

^IIPharmacy student at Pontifícia Universidade Católica do Rio Grande Sul - PUC-RS and Scholarship from the Cytogenetics Laboratory of UFCSPA, Porto Alegre, RS, Brazil

^IIIBiomedical Degree - Master's Degree student in Pathology at UFCSPA, Porto Alegre, RS, Brazil

^IVPediatric Cardiologist of Hospital da Criança Santo Antonio - HCSA/Complexo Hospitalar Santa Casa de Porto Alegre - CHSCPA, Porto Alegre, RS, Brazil

^VGeneticist of UFCSPA/Complexo Hospitalar Santa Casa de Porto Alegre - CHSCPA; Professor of Clinical Genetics and of the Pathology Post-graduation Course of UFCSPA, Porto Alegre, RS, Brazil

^VIBiologist, Professor, and Cytogeneticist responsible for the Cytogenetics Laboratory of the Medical Oncology Division, University of Colorado Denver, USA

^VIIGeneticist of UFCSPA/Complexo Hospitalar Santa Casa de Porto Alegre - CHSCPA; Professor of the Clinical Genetics Department and Pathology Post-graduate Course, and Cytogeneticist responsible for the Cytogenetics Laboratory of UFCSPA, Porto Alegre, RS, Brazil

Corresponding author

ABSTRACT

OBJECTIVE: To investigate the frequency of 22q11 deletion syndrome (22q11DS) in patients with complex congenital heart disease.

METHODS: A prospective and consecutive cohort of patients with complex heart defects was evaluated in their first hospitalization at a cardiac intensive care unit of a pediatric hospital. For each patient, an assessment form was completed with demographic information and clinical evaluation. High resolution karyotyping and fluorescence in situ hybridization (FISH) to detect the presence of 22q11 microdeletion, were performed. Heart defects were classified by a cardiologist.

RESULTS: The sample cohort consisted of 66 patients. Karyotypic anomalies were observed in 5 patients (7.6%); however, none of them had 22q11 deletion. Evaluation by FISH was successfully done in 65 patients, identifying 22q11 microdeletion in two patients (3.1%). Out of the 66 patients with complex defects, 52 were carriers of conotruncal malformations and in 51 patients, analysis for 22q11 microdeletion by FISH was performed. The two patients with 22q11 microdeletion belonged to this group, representing a frequency of 3.9%. They had tetralogy of Fallot.

CONCLUSION: 22q11DS is a frequent abnormality among patients with complex and conotruncal heart defects. Variations of the 22q11DS frequency among studies seem to be mainly associated with criteria used for patient selection and specific characteristics of the population analyzed.

Keywords: DiGeorge syndrome; in situ hybridization; fluorescence; heart defects; congenital, chromosomes; human; pair 22.

Introduction

Congenital cardiac malformations represent a heterogeneous group of diseases with variable hemodynamic consequences and, therefore, with different follow-up and intervention needs. Among these malformations, we high-light the complex heart defects, particularly for its severity. Also within this subgroup are the conotruncal heart defects characterized by changes in the heart outflow tract. These correspond to approximately 50% of congenital cardiopathies seen in newborns1, representing an important association with genetic disorders, especially 22q11 deletion syndromes (22q11DS, OMIM #188400/#192430)², also known as velocardiofacial syndrome or DiGeorge syndrome^3,4.

This syndrome is characterized clinically by a high phenotypic variability, without pathognomonic findings, hindering its diagnosis. It is due to a deletion in the region 11 of the long arm of chromosome 22 (i.e., 22q11), being an autosomal dominant disorder affecting families, i.e., an affected individual has a 50% chance of transmitting it to his/her children. As for its diagnosis, high-resolution karyotyping has limitations and is able to identify less than 15% of affected patients. Fluorescence in situ hybridization (FISH), which can detect over 90% of the cases, is considered the gold standard^5,6.

Therefore, due to the almost non-existence of related studies among us and the variability of the indices observed in literature, the objective of the present study was to determine the frequency of 22q11DS among patients with complex heart defects.

Methods

This study was performed on a prospective and consecutive cohort of patients in their first hospitalization due to congenital cardiac malformation in the Cardiological Intensive Care Unit (CICU) of Hospital da Criança Santo Antonio (HCSA)/Complexo Hospitalar Hospital Santa Casa de Porto Alegre (CHSCPA) during one year. This cohort was part of the study by Rosa et al. For each patient, an assessment form with clinical data, such as gender, age, race, precedence, reason for admission, and cardiological diagnosis was completed. Description of cardiac malformations, as well as their classification into complex and conotruncal defects was performed by a cardiologist participating in the study, always taking into consideration the results of echocardiogram, cardiac catheterization, and description of the cardiac surgery. Patients also underwent high resolution band karyotyping (> 550 bands) and fluorescence in situ hybridization to detect 22q11 microdeletion using the commercially available DNA probe DiGeorge/VCFS Region Probe (TUPLE 1), followed by a standard codenaturation protocol.

The SPSS (version 12.0) and PEPI (version 4.0) softwares were used for data processing and analysis. Fischer's exact test was used to compare the frequencies observed in our study and in literature. Values of p < 0.05 were considered significant. This study was approved by the Research Ethics Committee of UFCSPA and CHSCPA.

Results

Out of 207 patients with congenital cardiopathies hospitalized for the first time in the CICU, and whose guardians consented to their participation in the study, 66 (31.9%) had complex malformations. Forty-three were males (62.5%) and 23 females (34.8%), and the majority were Caucasians (77.3%). Their ages ranged from 1 day to 10 years (51% were younger than 1 month). Most patients were from the country side of Rio Grande do Sul State (59.1%), and cardiac surgery was the main reason for CICU admission (74.2%). Heart defects presented by the patients are listed in Table 1. Tetralogy of Fallot (30.3%) was the most important of these defects. As for karyotyping, changes were observed in five patients (7.6%): four with free chromosome 21 trisomy, and one with free chromosome 18 trisomy. No case of 22q11 deletion was identified by this examination. Analysis using FISH technique was successfully performed in 65 patients, identifying 22q11 microdeletion in two cases (3.1%) (two patients with tetralogy of Fallot). Out of 66 patients with complex cardiac defects, 52 patients had conotruncal defects, and 51 of them underwent investigation for 22q11 microdeletion. The two patients with 22q11 microdeletion were in this group, representing a frequency of 3.9% (2/51) (Table 2).

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Discussion

In our literature review, we found only one study evaluating the frequency of 22q11DS among patients with complex heart defects. Mehraein et al.⁷, evaluating a cohort of 40 patients, observed a deletion index of 22.5%. This was significantly higher than in our study (3.1%). We believe that this might be related to selection criteria in the first study, which evaluated a cohort originated from departments of clinical genetics and pediatric cardiology in Germany.

It is known that 22q11DS has an important relationship with conotruncal defects³, and, in our cohort, 52 out of 66 (78.8%) patients with complex congenital cardiopathy had this defect. They represented all individuals with conotruncal defect in the initial cohort of 207 patients. The frequency of 22q11DS in our study (3.9%) was similar to other indices, which are between 4% and 15%^4,8-15, but different from others who reported indices between 17% and 49%^1,16-20 (Table 2). These differences seem to be particularly related to the age of patients, their precedence, and frequency of specific heart defects, such as interruption of the aortic arch, which, among the conotruncal malformations, is associated even more with 22q11DS.

Iserin et al.¹ described a higher index of 22q11DS (48%) when evaluating newborns seen in a pediatric cardiology service in France, who presented with conotruncal defects more commonly associated with this syndrome (Table 2). It is known that these are severe defects and, depending on the age of evaluation and place of birth, individuals might not be alive to be evaluated, as suggested by Rosa et al.³. This situation is even worse in places where prenatal diagnosis of congenital cardiopathies is inadequate and there is not an appropriate infrastructure for adequate care and treatment of those patients, as in our case³. On the other hand, Voigt et al.¹¹, who found a frequency of SD22q11 quite similar to our work (4%), evaluated a group of patients who underwent cardiac catheterization in a cardiology center in Germany. Note that these patients were characterized by more advanced age, ranging from 4 days to 58 years (mean 6.1 years), a high frequency of transposition of great vessels (a defect with little association with 22q11DS), and absence of aortic arch interruption, similar to what was observed in our cohort (Table 2).

Most of these studies do not describe patients with different chromosomal abnormalities other than 22q11DS. In our study, patients with Down's syndrome and Edwards' syndrome were identified. In this case, we do not know whether it is related to type of patient selection or even the population characteristics, since in many cases, those studies were performed in countries where, unlike Brazil, gestational interruption in cases of fetus with chromosomal anomalies is allowed. Thus, these aspects could interfere with the frequencies observed among individuals in the postnatal period. On the other hand, in other studies, such as Worthington et al.¹⁹, patients with chromosomal abnormalities, or even those with an identifiable non-22q11DS syndrome, were excluded (Table 2).

Conclusion

In conclusion, 22q11DS is a common abnormality among patients with complex congenital heart and conotruncal defects. Variations between studies seem to be associated mainly with the selection process and characteristics of the population. Identification of these patients is essential for their adequate management and genetic counseling.

Acknowledgments

We are thankful to the Cordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for the grant received.

References

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