Flashcards in Skin 4 - Disorders of Pigmentation and Melanocytes Deck (44)
What are the disorders of pigmentation and melanocytes?
1) vitiligo 2) albinism 3) Freckle (ephelis) 4) melasma 5) nevus (mole) 6) melanoma
What are melanocytes responsible for?
Where are melanocytes located?
They are present in the basal layer of the epidermis.
What are melanocytes derived from?
the neural crest
What do melanocytes do?
Synthesize melanin in melanosomes using tyrosine as a precursor molecule
What do melanocytes do?
They pass melanosomes to keratinocytes
What is vitiligo?
Localized loss of skin pigmentation
What is vitiligo due to?
autoimmune destruction of melanocytes
What happens in albinism?
It is a congenital lack of pigmentation
What is albinism due to?
an enzyme defect (usually tyrosinase) that impairs melanin production
What might albinism involve?
May involve the eyes (ocular form) or both the eyes and skin (oculocutaneous form)
What is there an increased risk for in albinism and why?
Increased risk of squamous cell carcinoma, basal cell carcinoma, and melanoma due to reduced protection against UVB
What is freckle?
(ephelis) small, tan to brown macule; darkens when exposed to sunlight
What is freckle due to?
increased number of melanosomes (melanocytes are not increased)
What is melasma?
mask-like hyperpigmentation of the cheeks
What is melasma associated with?
pregnancy and oral contraceptives
What is nevus?
(mole) benign neoplasm of melanocytes
What is congenital nevus?
it is present at birth; often associated with hair
When do you see acquired nevus?
it arises later in life.
How does a nevus begin?
Begins as nests of melanocytes at the dermal-epidermal junction (junctional nevus);
What is the most common mole in children?
What is a compound nevus?
When the nevus grows by extension into the dermis
What is an intradermal nevus?
The junctional component is eventually lost resulting in an intradermal nevus, which is the most common mole in adults.
What is the most common mole in adults?
What is a nevus characterized by?
Characterized by a flat macule or raised papule with symmetry, sharp borders, evenly distributed color, and small diameter (< 6 mm)
What might arise from a nevus?
Dysplasia may arise (dysplastic nevus), which is a precursor to melanoma
What is melanoma?
Malignant neoplasm of melanocytes; most common cause of death from skin cancer
What is the most common form of death from skin cancer?
What are the risk factors for melanoma?
They are based on UVB-induced DNA damage and include prolonged exposure to sunlight, albinism, and xeroderma pigmentosum; an additional risk factor is dysplastic nevus syndrome,