OBJECTIVETo explore the genotype-phenotype correlation of a child with chromosome 18q deletion syndrome.

METHODSG-banded karyotyping, single nucleotide polymorphism array (SNP array) and fluorescence in situ hybridization (FISH) were performed on the child with abnormal phenotypes. Genotype-phenotype correlation was explored following accurate mapping of the breakpoints on chromosome 18q. SNP array was also performed on the genome DNA derived from peripheral venous blood samples from both parents.

RESULTSChromosomal analysis revealed that the child has a karyotype of 46, XY, del(18) (q23). SNP array analysis detected a 9.855 Mb deletion (chr18: 68 158 880-78 014 123) at 18q22.2q23. Mapping of the breakpoints suggested that the deletion has overlapped with that of distal chromosome 18q deletion syndrome and encompassed several critical regions for this syndrome. SNP array performed on parental samples suggested that the 18q22.2q23 deletion was de novo in origin. FISH analysis of peripheral blood sample from the child confirmed the presence of 18qter deletion.

CONCLUSIONThe phenotype of this child may be attributed to the deletion of distal 18q22.2q23, which has encompassed several critical regions for the 18q deletion syndrome.