OBJETIVO: O uso clínico de técnicas baseadas em microarrays para a análise de transtornos de desenvolvimento tem surgido durante a última década. Assim, o microarray cromossômico tem sido posicionado como um teste de primeiro nível clínico. Relatamos a primeira experiência em uma coorte chilena. MÉTODOS: Pacientes chilenos com atraso de desenvolvimento e anomalias congênitas foram estudados com um microarray de alta densidade (CytoScan(tm) HD Array, Affymetrix, Inc., Santa Clara, CA, EUA). Pacientes tiveram estudos citogenéticos anteriores, ou um resultado normal ou de uma anomalia não bem caracterizada. RESULTADOS: Foram analisados 40 pacientes selecionados por dois ou mais critérios, incluindo: anomalias congênitas maiores, dismorfismo facial, atraso de desenvolvimento e deficiência intelectual. Uma variante do número de cópia (CNV) foi encontrada em 72,5% dos pacientes, enquanto que uma CNV patogênica foi encontrada em 25% dos pacientes e uma CNV de significado clínico incerto foi encontrada em 2,5% dos pacientes. CONCLUSÕES: A análise cromossômica microarray é uma ferramenta útil e poderosa em transtornos de desenvolvimento, permite um diagnóstico preciso, melhora a taxa de diagnóstico e descobre novas etiologias. O custo mais elevado é uma limitação para um uso difundido em nossa realidade.

OBJECTIVES: Clinical use of microarray-based techniques for the analysis of many developmental disorders has emerged during the last decade. Thus, chromosomal microarray has been positioned as a first-tier test. This study reports the first experience in a Chilean cohort. METHODS: Chilean patients with developmental disabilities and congenital anomalies were studied with a high-density microarray (CytoScan(tm) HD Array, Affymetrix, Inc., Santa Clara, CA, USA). Patients had previous cytogenetic studies with either a normal result or a poorly characterized anomaly. RESULTS: This study tested 40 patients selected by two or more criteria, including: major congenital anomalies, facial dysmorphism, developmental delay, and intellectual disability. Copy number variants (CNVs) were found in 72.5% of patients, while a pathogenic CNV was found in 25% of patients and a CNV of uncertain clinical significance was found in 2.5% of patients. CONCLUSION: Chromosomal microarray analysis is a useful and powerful tool for diagnosis of developmental diseases, by allowing accurate diagnosis, improving the diagnosis rate, and discovering new etiologies. The higher cost is a limitation for widespread use in this setting.

Microdeletion 22q11 in humans causes velocardiofacial and DiGeorge syndromes. Most patients share a common 3Mb deletion, but the clinical manifestations are very heterogeneous. Congenital heart disease is present in 50-80% of patients and is a significant cause of morbidity and mortality. The phenotypic variability suggests the presence of modifiers. Polymorphisms in the VEGFA gene, coding for the vascular endothelial growth factor A, have been associated with non-syndromic congenital heart disease, as well as with the presence of cardiovascular anomalies in patients with microdeletion 22q11. We evaluated the association of VEGFA polymorphisms c.-2578C>A (rs699947), c.-1154G>A (rs1570360) and c.-634C>G (rs2010963) with congenital heart disease in Chilean patients with microdeletion 22q11. The study was performed using case-control and family-based association designs. We evaluated 122 patients with microdeletion 22q11 and known anatomy of the heart and great vessels, and their parents. Half the patients had congenital heart disease. We obtained no evidence of association by either method of analysis. Our results provide further evidence of the incomplete penetrance of the cardiovascular phenotype of microdeletion 22ql 1, but do not support association between VEGFA promoter polymorphisms and the presence of congenital heart disease in Chilean patients with this syndrome.

Cystic fibrosis (CF) is caused by mutations in the CFTR gene. More than 1600 mutations have been described, with frequencies that differ worldwide according to the ethnic origin of patients. A small group of mutations are recurrent on several populations. It has been shown that they each tend occur on specific chromosome 7 haplotypes, supporting the notion of a single origin for them. Less than 50% of mutations in Chilean patients have been identified to date. To indirectly assess the possible presence of a predominant founder mutation in the remaining unknown alíeles, we evaluated 2 polymorphic markers, XV-2c and KM.19, tightly linked to the CFTR locus. The study was done in Chilean CF patients with unknown or delt F508 ( F508) CFTR mutations and their haplotypes were compared to affected family-based controls. F508 showed marked linkage disequilibrium with XV-2c/KM.19 haplotype B, with 90% of alíeles on that haplotype. There was no difference in haplotype distribution between unknown mutations and normal controls. These results support a European origin for F508 alíeles in Chilean patients, and make unlikely the presence of a predominant founder mutation in the so-far unknown alíeles

Genomic imprinting is a reversible phenomenon that affects the expression of genes depending on their parental origin. The best characterized human disorders resulting from an alteration of the imprinting process are Angelman and Prader-Willi syndromes. They are due to the lack of active maternal or paternal genes, respectively, from chromosome region 15q11q13. Most cases arise via interstitial deletions. We review evidence that other common cytogenetic alterations of this region, interstitial and supernumerary duplications, could be the reciprocal products of the deletions and are also affected by the imprinting phenomenon, given the predominance of maternally-derived duplications in patients ascertained due to developmental delays or autistic features.