There are other types of lentigo other than solar lentigo. The simple lentigo, for example, is a lentigo that occurs in a large number of people with light skin or red hair.
Simple lentigo develops in childhood or as a young adult and reduces as you get older. They are smaller than solar lentigo and are around 3-5mm in diameter. Unlike solar lentigo, simple lentigo may occur on any part of the body and are not sun-induced.
A small number of people with numerous simple lentigo (also called lentigo simplex) have a hereditary condition called Peutz-Jeghers Syndrome. The spots of Peutz-Jeghers syndrome also occur inside the mouth. Most research link this condition with benign vascular growth inside the gastrointestinal tract. These hamartomas may bleed and cause anaemia.