091714 melanocytes

Question 1

what types of cells are melanocytes?

Answer 1

dendritic cells with dendrites extending to multiple keratinocytes to facilitate melanosome transfer

Question 2

what is pigmentation of skin dependent on?

Answer 2

size, number and density of melanosomes (pigment granules in keratinocytes)

Question 3

Wood’s light

Answer 3

used to differentiate light from white areas of skin

Question 4

tuberous sclerosis

Answer 4

autosomal dominant genetic disorder
causes non malignant tumors of brain, eyes, heart, kidney, skin, lungs

TSC1 (hamartin) and TSC2 (tuberin) mutations

Question 5

vitiligo

Answer 5

autoimmune disorder
destruction of melanocytes and depigmented patches

often symmetric involvement

Question 6

oculocutaneous albinism

Answer 6

inherited genetic disorder

absence or marked reduction of pigment in skin, hair, eyes

Question 7

what is the pathogenesis of oculocutaneous albinism

Answer 7

defect in melanin production

Question 8

what are oculocutaneous albinism pts at risk for

Answer 8

skin cancer b/c melanin plays protective role against photodamage

Question 9

ephelides

Answer 9

freckles

Question 10

what helps differentiate ephelides from other pigmented lesions?

Answer 10

they darken w sun exposure

Question 11

cafe au lai macules

Answer 11

well circumscribed
uniformly light to dark brown macules or patches

not uncommon to have a few
multiple ones are rare though

Question 12

solar lentigines

Answer 12

tan to dark brown or black macule due to UV irradiation

in contrast to ephelides, these are seen later in life and often bigger (5-15 mm)

occur in sites of sun exposure. may darken w/ sun exposure

Question 13

dermal melanocytosis

Answer 13

blue-gray patches over lumbosacral region of infants w/ darker skin types

historically referred to as Mongolian spots

pigment usually fades w/ age
tend to be larger patches

Question 14

what are some genetic diseases associated w/ pigmented or hypopigmented lesions?

Answer 14

neurofibromatosis type 1

tuberous sclerosis

Question 15

neurofibromatosis type 1 is caused by mutations in what gene

Answer 15

NF1 gene enconding neurofibromin

Question 16

what do pts w/ neurofibromatosis type 1 have on their skin?

Answer 16

multiple cafe au lait macules starting in childhood
axillary and inguinal freckling
with time, neurofibromas can develop in skin–look like soft or rubbery papules

plexiform neurofibromas-larger plaques that have a bag of worms feel

Question 17

tuberous sclerosis results in

Answer 17

benign tumor formation in multple organ systems

Question 18

tuberous sclerosis is caused by mutations in

Answer 18

TSC1 and TSC2, encoding hamartin and tuberin

Question 19

skin involvement of tuberous sclerosis

Answer 19

facial angiofibromas–telangiectatic papules that develop on the central face

periungual fibromas (similar lesions found along nail folds)

hypomelanotic macules and patches (ash leaf macules) can be present in early childhood