Chromosome 4q duplication is a chromosome abnormality characterized by an extra copy (duplication) of genetic material on the long arm (q) of chromosome 4. The severity and specific symptoms depend on the size and location of the duplication, and which genes are involved. Features that have been described in some people with chromosome 4q duplication include developmental delay, intellectual disability, behavioral problems, birth defects, and distinctive facial features. Most cases are inherited from an unaffected parent with a chromosomal rearrangement called a balanced translocation. Some cases are not inherited and occur sporadically. Treatment is based on the signs and symptoms present in each person.