The chromosome 18 conditions are a collection of conditions caused by missing or duplicated segments of chromosome 18. These segments can be different sizes and from different locations of the chromosome. Consequently, those affected can have from mild to profound disabilities. Common challenges include learning disability, hearing or vision impairment, autism, heart disease, autoimmune disorders or neuromuscular disorders. We group these chromosome changes in to five clusters, 18p- (a missing piece of the chromosome short arm), 18q- (a missing piece of the chromosome long arm), Tetrasomy 18p (4 copies of the chromosome short arm), Ring 18 (one copy of the chromosome is ring shaped) and Trisomy 18 (3 copies of chromosome 18).