A novel 800 kb microduplication of chromosome 16q22.1 resulting in learning disability and epilepsy may explain phenotypic variability in a family with 15q13 microdeletion.

The phenotype of 15q13.3 microdeletion is variable and can be non-penetrant. Recently, "second-hit hypothesis" has been proposed as a possible explanation for some variability in recurrent microdeletion syndromes. We present a family with a 1.9 Mb 15q13.3 deletion and a novel 800 kb 16q22.1 duplication. We show that the 16q22.1 duplication may be a phenotypic modifier in this family and likely results in epilepsy and learning difficulties. We state the possible genes in this region that may be important in neurological development and function.