Final answer:
A congenital condition of the skin with abnormal light patches is known as vitiligo, a result of depigmentation due to an autoimmune response affecting melanocytes.
Step-by-step explanation:
A congenital condition of the skin consisting of abnormal light patches is called vitiligo. Individuals with vitiligo experience depigmentation, leading to the formation of lighter colored patches of skin, which is particularly noticeable on darker skin. This condition may be caused by an autoimmune reaction where melanocytes in certain areas lose their capability to produce melanin, the pigment that determines skin color and helps protect against UV radiation.
Other skin conditions that result in pigment changes include albinism, which is a genetic disorder leading to very pale skin, and xeroderma pigmentosum, a condition where damage from UV light exposure is not properly repaired, leading to skin lesions. It is important to address the symptoms of these disorders for individual health and protection against further skin damage.