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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