Question: What is (are) 15q11.2 microdeletion ?
Answer: 15q11.2 microdeletion refers to a chromosome abnormality in which a tiny piece of genetic material on the long arm of chromosome 15 (at a location designated q11.2) is missing (deleted). The features of people with a 15q11.2 microdeletion vary widely. The most common features include developmental, motor, and language delays; behavior and emotional problems; attention deficit disorders; and autism spectrum disorder. Other features may include birth defects and seizures. However, some people have no apparent physical, learning, or behavior problems. A 15q11.2 microdeletion may occur randomly for the first time in an affected person, or it may be inherited from a parent. Treatment depends on the signs and symptoms in each person.
Source: GARD

Question: What causes 15q11.2 microdeletion ?
Answer: What causes a 15q11.2 microdeletion? A 15q11.2 microdeletion may occur randomly for the first time in an affected person (a de novo mutation), or it may be inherited from a parent with the microdeletion. A blood test to look at the parents' chromosomes is needed to find out how the microdeletion occurred. When a 15q11.2 microdeletion occurs as a de novo mutation, it is due to a random error - either during the formation of a parent's egg or sperm cell, or very soon after conception (fertilization of the egg). A parent with the microdeletion has a 50% chance with each pregnancy to pass on the microdeletion. The features of 15q11.2 microdeletion occur because the deleted region of the chromosome contains several genes that are important for normal growth and development. It is not yet clear why there is a large range of features and severity among people with a 15q11.2 microdeletion, or why some people are unaffected.
Source: GARD