Disorders of Pigmentation and Melanocytes

Question 1

What are melanocytes responsible for and where are they present in the skin?

Answer 1

Skin pigmentation; Basal layer of epidermis

Question 2

What are melanocytes derived from?

Answer 2

Neural crest cells

Question 3

How do melanocytes function?

Answer 3

They synthesize melanin in melanosomes using tyrosine as a precursor molecule and pass melanosomes to keratinocytes

Question 4

What is vitiligo?

Answer 4

Localized loss of skin pigmentation do to autoimmune destruction of melanocytes

Question 5

What is albinism?

Answer 5

Congenital lack of pigmentation due to enzyme defect that impairs melanin production

Question 6

What are the two types of albinism?

Answer 6

Ocular and oculocutaneous

Question 7

What conditions do albinism increase your risk for?

Answer 7

SCC, BCC and melanoma due to UVB

Question 8

What is another name for a freckle? What is a freckle? What gives freckle its characteristic appearance?

Answer 8

Ephelia; Small tan brown macule that darkens when exposed to light due to increased melanosomes (melanocytes are NOT increased)

Question 9

What is a melasma? What is melasma associated with?

Answer 9

Mask-like hyperpigmentation of the cheeks associated with pregnancy and oral contraceptives

Question 10

What is a nevus?

Answer 10

Benign neoplasm of melanocytes associated with hair characterized as a flat macule or raised papule with symmetry, sharp borders, evenly distributed color and small diameter (<6 mm); Nevus can be congenital or acquired

Question 11

Describe to process of acquired nevus formation

Answer 11

Begin as nest of melanocytes at the dermal-epidermal junction which grows by extension into the dermis. Junctional component eventually lost resulting in an intradermal nevus, which is the most common mole in adults

Question 12

What can a dysplastic nevus lead to?

Answer 12

Melanoma

Question 13

What is melanoma?

Answer 13

Malignant neoplasm of melanocytes; MOST common cause of death from skin cancer

Question 14

What are risk factors for melanoma?

Answer 14

UVB-induced DNA damage, prolonged exposure to sunlight, albinism, xeroderma pigmentosum, dysplastic nevus syndrome (Autosomal dominant disorder characterized by formation of dysplastic nevi)

Question 15

What are the ABCDs of melanoma?

Answer 15

Asymmetry, Borders irregular, Color not uniform, Diameter >6 mm

Question 16

What are the two growth phases of melanoma?

Answer 16

1) Radial growth along dermis and superficial epidermis (low risk for metastasis) 2) Vertical growth into the deep dermis resulting in increased risk of metastasis

Question 17

What is the most important prognostic factor in predicting melanoma prognosis?

Answer 17

Breslow thickness (depth of extension)

Question 18

What is the most common subtype of melanoma?

Answer 18

Superficial spreading resulting in dominant early radial growth (good prognosis)

Question 19

What is lentigo maligna melanoma?

Answer 19

Lentiginous proliferation along epidermal-dermal junction (good prognosis)

Question 20

What is nodular melanoma?

Answer 20

Early vertical growth (poor prognosis)

Question 21

What is Acral Lentiginous melanoma?

Answer 21

Melanoma arising on pals or soles often in dark-skinned individuals; Not related to UV exposure