Clinical report: variable phenotypic expression in a large sibling cohort with a deletion of 4p16.1.

We report a half-sibling cohort with deletion of 4p16.1, astigmatism, gross and fine motor delay, variable intellectual disability, and variable behavioral concerns. However, two siblings without the deletion also had learning delays and psychological concerns. Thus, variable phenotypic expression was seen and the significance of deletion of 4p16.1 remains unclear.