Hereditary predisposition is believed to be a contributing factor in the development of preauricular sinus, as it is a genetic malformation. This malformation is thought to occur due to abnormalities in the formation of the branchial ridges during fetal development. Normally, these ridges develop into various structures, including the ears. However, in the case of preauricular sinus, the branchial ridges may remain separate from the rest of the system and form the sinus.