OBJECTIVETo explore the candidate disease causing gene for a case with floppy infant syndrome (FIS).

METHODSSingle nucleotide polymorphism array (SNP array) was used for analyzing the whole genome copy number mutations in the proband. Multiple PCR combined with denaturing high performance liquid chromatography (DHPLC) was employed to verify the suspected mutations in the proband and his family members.

RESULTSA large duplication arr [hg19] Xq13.1: 67 987 646-73 805 828, which spans approximately 5.818182 Mb and encompasses 66 known genes, was identified in the proband. The multiple PCR-DHPLC assay confirmed duplication of HDAC8, PHKA1, TAF1, DLG3, KIF4A, IGBP1, PJA1 and SLC16A2 genes in the proband. His mother and grandmother both had duplication of the above genes in one X chromosome, but his aunt had not.

CONCLUSIONThe large Xq13.1 duplication identified by the SNP array probably underlies the FIS in this family. For its high-throughput, high resolution and capacity of automation, SNP array has provided a first line method for the genetic testing for infants featuring developmental delay with unknown reason, mental retardation, autism, multiple malformation and FIS.