Hypopigmentation means the body does not produce enough melanin. Albinism, for example, is an inherited condition that causes a lack of pigment. So people with albinism typically have light skin, white or pale yellow hair, and light blue or gray eyes. Another condition called vitilgo, creates smooth, depigmented white spots on the skin. Vitilgo affects nearly 2% of the population, but it strikes people between 10 and 30 years old more often, and is more evident in people with darker skin.

Generalised reduction in pigmentation

Generalised reduction in pigmentation at birth (congenital) may be racial in origin or due to albinism. Pituitary failure resulting in lack of MSH rarely results in acquired hypomelanosis (pallor is much more frequently due to blood loss or anaemia).

Localised hypopigmentation

Localised hypopigmentation may be due to partial or complete loss of melanin (achromia or leukoderma).

Decreased levels of melanin results mainly from two different types of changes:

• decreased numbers or absence of melanocytes in the epidermis resulting in little or no melanin production (melanocytopenic hypomelanosis, e.g. vitiligo), and
• no decrease in the number of melanocytes but decreased levels of melanin production (melanopenic hypomelanosis).

In more detail:

• Abnormal migration/differentiation of melanoblasts – piebaldism
• Destruction of melanocytes – vitiligo
• Reduced tyrosinase activity – ocular cutaneous albinism type 1A
• Abnormal structure of melanosomes – Chediak-Higashi syndrome, progressive macular hypomelanosis
• Reduced melanization and/or numbers of melanosomes – albinism (tyrosinase positive variants), tuberous sclerosis, hypopigmentosis of Ito
• Reduced transfer to keratinocytes/increased degradation of melanosomes within melanocytes – postinflammatory leukoderma