OBJECTIVETo determine the genetic cause for two mentally retarded patients from a family, and to correlate their genotypes with clinical phenotypes.

METHODSRoutine G-banded karyotyping analysis was performed. Single nucleotide polymorphism (SNP) microarray analysis was used to detect microdeletions or microduplications. Fluorescence in situ hybridization (FISH) was used to ascertain the origin of chromosomal abnormalities.

RESULTSBoth proband and his uncle showed a normal karyotype. SNP microarray analysis has identified a 1.147-Mb microdeletion at 16p13.3 (85 880-1 233 819) and a 2.948-Mb microduplication at 19q13.42-q13.43 (56 008 597-58 956 816). FISH analysis confirmed that the patient has inherited a derivative chromosome 16 from his father. The proband presented with mental retardation, reduced speech, and facial dysmorphism (hypertelorism, down-slanting palpebral fissure, low nasal bridge and wide gap between front teeth). His uncle presented with a milder phenotype with mental retardation.

CONCLUSIONBoth the proband and his uncle have carried a chromosome microdeletion at 16p and microduplication at 19q, which were originated from their fathers carrying a balanced t(16;19) translocation. Combined SNP microarray analysis and FISH assay are useful for the detection the copy number variations and delineation of potential structural changes, which may help with evaluation of recurrence risk for this family.