The age of onset is the age at which an individual acquires, develops, or first experiences a condition or symptoms of a disease or disorder. For instance, the general age of onset for the spinal disease scoliosis is "10-15 years old,"[1] meaning that most people develop scoliosis when they are of age between ten and fifteen years.
Diseases are often categorized by their ages of onset as congenital, infantile, juvenile, or adult. Missed or delayed diagnosis often occurs if a disease that is typically diagnosed in juveniles (such as asthma) is present in adults, and vice versa (such as arthritis).[2] Depending on the disease, ages of onset may impact features such as phenotype, as is the case in Parkinson's and Huntington's diseases.[3][4] For example, the phenotype for juvenile Huntington's disease clearly differs from adult-onset Huntington's disease and late-onset Parkinson's exhibits more severe motor and non-motor phenotypes.[3][4]