Abstract
Chromosome 22 is the second smallest human chromosome, covering more than 51 million base pairs and comprising between 1.5% and 2% of the total DNA in cells. Microdeletion of chromosome 22q11.2 underlies the most commonly diagnosed human deletion syndrome and is associated with over 180 clinical features. The condition is highly underdiagnosed in developing countries and diverse population groups. A variety of laboratory techniques have been used over the years to detect the 22q11.2 microdeletion, resulting in the discovery that more than one gene on chromosome 22 is involved. Many patients with the syndrome now survive into adulthood. The clinical and genetic manifestation of this syndrome is present in all medical disciplines with care for both adults and children being relatively intricate. Genetic counselling involves increasing a family’s knowledge about the condition, laboratory testing, and related procedures. This review describes the clinical features and findings, some of the molecular genetics, genetic counselling, and laboratory techniques that have evolved over the years in the diagnosis of the 22q11.2 deletion syndrome.