Lentigines (liver spots) are the result of oxidation (burning of tissue from oxygen) of your pigmented skin cells. Consequently, lentigines occur in areas of your skin where there is an excessive amount of concentrated melanin (skin pigment) and excessive sun exposure. These darkened hyperpigmented lesions are most often noticeable in people with a fair complexion (Fitzgerald Classification I and II).
Lentigines are quite common and our found in people with varying ethnicity. However, you can definitely be genetically predisposed to developing lentigines over the course of your life. One specific gene related to the predilection towards developing lentigines is called the melanocortin-1 receptor MC1R gene variant. Those genetically predisposed will likely develop these discrete hyperpigmented lesions after prolonged exposure to sunlight. Natural sunlight contains specific light frequencies call UV-B that then activates your melanocytes (melanin producing cells) to produce melanin and hence cause discrete areas of hyperpigmentation in locations where you have excessive melanin (skin pigment)
Lentigines are predominantly found on areas of your skin that are frequently exposed to the sun. These susceptible locations include your face, arms, and shoulders.