New microdeletion syndromes

The widespread use of chromosome microarray analysis (CMA) has led to the detection of previously unrecognized microdeletion and microduplication syndromes often caused by nonallelic homologous recombination between blocks of segmental duplication. In this review, we provide clinical and molecular cytogenetic description of the more recently described microdeletion syndromes with well delineated clinical phenotype: 17q21.31 deletion syndrome, 22q13.3 deletion syndrome, 15q24 deletion syndrome and 9q34.3 deletion syndrome. As some microdeletions/microduplications are described in individuals with normal phenotype, additional studies are necessary to further evaluate their clinical spectrum and penetrance. Genetic counseling is required for all tested families, especially in view of the presence of copy number variants of uncertain clinical consequences, incomplete penetrance, or variable expressivity.

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