Melanocytic Disorders

Solar lentigo

• Common finding in elderly individuals
• Brown, macules located on sun-exposed areas ("liver spots“-on the back of the hands, and face)
• Increased number of melanocytes which produce excessive melanin.
• Not precancerous
• No treatment is required

Freckles

• Focal overproduction of melanin with normal number of melanocytes with increase in melasosomes.
• Freckles are sharply demarcated light brown-ginger macules of upto 5mm in diameter due to over production of melanin.
• Most prominent in sun exposed sites, and multiply and become darker with sun exposure

Vitiligo

• Common in blacks
• Autoimmune destruction of melanocytes
• Causes extensive areas of skin depigmentation 
• Often associated with other autoimmune conditions like diabetes, thyroid and adrenal disorders and pernicious anemia.

Clinical features

• Segmental vitiligo- is restricted to one part of the body, but necessarily a dermatome.
• Generalised vitiligo- is often symmetrical and involves the hands, wrists, knees, neck and area around the body orifices.
• The hair of the scalp and beard may also depigment.
• The patches of depigmentation are sharply defined.

Treatment

• Protecting the patches from excessive sun exposure with clothing and sunscreen- helps in reducing episodes of burning and potentially of skin cancer.
• Potent topical corticosteroids
• Phototherapy with PUVA

Albinism

It occurs when the melanocytes are unable to synthsize melanin ( either by absence of tyrosinase activity or inability of cells to take up tyrosine)

Melasma

Macular, hyperpigmented lesions on the forehead and cheeks 

Female predominance; exacerbated (melanocytes produce more melanin) by:

a. Oral contraceptives (OCP)

b. Pregnancy ("pregnancy mask")

c. Sunlight

Treatment

Application of hydroquinone (bleaching agent) to skin