Humans share the same genes but do not have iden- tical DNA sequences. The latest 1000 genomes project re- ported over 84.4 million single nucleotide polymorphisms (SNPs), 3 million short insertions/deletions, and 60,000 structural variants in 2,504 subjects from 26 populations (1000 genomes project consortium 2015) (1). One of the most significant outcomes of identification of these dier- ences is the development of personalized medicine. The vision of personalized medicine is based on using an individual's genetic profile to guide decisions made re- garding to the prevention, diagnosis, and make the best therapeutic. Pharmacogenetics, which also has been called individualized or precision medicine, has been widely rec- ognized as a fundamental step toward development of personalized medicine. It deals with the influence of ge- netic variants on treatment response or the risk of seri- ous adverse reactions to drugs. A great number of genetic variants are located in gene products that are involved in the metabolization, absorption, elimination and action of drugs. Single nucleotide variants as well as structural variants such as inversions and copy number variations (deletions and duplications) in these genes have been con- tributed to the drug response of individuals (2, 3). In the case of pediatrics, the impact of genetics on health and ill- ness has been appreciated for many years. For instance, Down syndrome as a congenital disease was well known in the nineteenth century. Numerous other examples of disease with genetics implications, such as cystic fibrosis and Duchenne muscular dystrophy, having a significant impact on children's health, well-being and life expectancy have been known for many decades. However, most of these genetic disorders were historically either chromoso- mal polysomies (for example, Down Syndrome) or disor- ders that are inherited by classical Mendelian or X-linked inheritance (for example, cystic fibrosis or Duchenne mus- cular dystrophy). In contrast, majority of variants with pharmacological consequences are involved in remark- ably more complex mechanisms and interactions of sev- eral genes and their products. A growing number of studies are being published on the impact of individual genetic background on drug re- sponse. However, most of these reports have dealt with adult individuals and only a few studies have investigated the role of pharmacogenetics in pediatrics, with high- lighting the importance of dierences between children and adults. A major obstacle for such pediatric studies is that both ontogeny and genetic variation contribute to variability in therapeutic response across dierent age