Prenatal detection of interstitial 18p11.31-p11.22 microduplications: Phenotypic diversity and literature review.

INTRODUCTION: Pure duplication of chromosome 18p is rare, with clinical phenotypes ranging from normal or slight abnormalities to various degrees of mental retardation. It remains difficult to establish a clear genotype-phenotype correlation. METHODS: Chromosomal karyotyping analysis was performed on cultured amniotic fluid cells from three cases. Single nucleotide polymorphism (SNP) array analysis was carried out using the Illumina Human CytoSNP-12 BeadChip. We also carried out a review of the literature regarding 18p11 microduplication. RESULTS: G-banding analysis showed that the three cases had normal karyotypes. SNP array results showed 0.48- to 1.6-Mb microduplications of 18p11.31-p11.22 (chr18: 6995739-8713088) in these cases, encompassing different degrees of LAMA1 duplication. Follow-up analysis showed that the parents of both cases 1 and 2 chose termination of pregnancy. Case 3 presented with normal growth and physical development. Currently, there is not enough evidence supporting the pathogenicity of LAMA1 triplosensitivity. CONCLUSION: We described three prenatal cases with 18p11.31-p11.22 microduplications involving part of the LAMA1 locus. There might be phenotypic diversity associated with 18p11.31-p11.22 microduplications. To avoid unnecessary abortions for pregnancies such as these, comprehensive genetic counseling should be offered.