Pediatric diseases are those that affect children during their developmental years. Experts in paediatric diseases assess and treat children with immune system abnormalities, both acquired and congenital, and can advise on travel vaccines. Specialists treat infants and children with infections caused by viruses, bacteria, fungi, or parasites, as well as infections that affect several body systems, infections that are unique or severe, and infections caused by aberrant or impaired immune systems, such as AIDS. In paediatric medicine, age is a crucial aspect to consider when examining phenotypic changes in health and disease states. Age-related illness patterns have been described by several studies. However, no data on how to categorise prevalent paediatric disorders into age categories has been published so far.