1.4 Disorders of Pigmentation and Melanocytes

Question 1

what are melanocytes derived from?

Answer 1

neural crest

Question 2

how to distinguish nevus from melanoma?

Answer 2

Use ABCD for melanoma criteria:

A: asymmetry

B: borders irregular

C: Color: not uniform

D: diameter: >6mm

Also, melanomas do not have hair in them, whereas many nevi do

Question 3

neurofibromatosis 1

-skin findings (3)

Answer 3

1. cafe au lait spots
2. axillary/inguinal freckling
3. neurofibromas

Question 4

melanoma

• what is it
• how does it progress?

Answer 4

• malignant tumor of melanocytes
• 2 growth phases:
  1. radial growth (spread along epidermis and dermis)
  2. vertical growth (spread into deep dermis, risk of metastasis)

Question 4

Tuberous sclerosis

-what is it

Answer 4

• auto dom disorder
• causes benign tumors of many organs (brain, eyes, heart, kidney, skin, lungs)

Question 7

chemical production of melanin (simplified)

Answer 7

tyrosine –> melanin

important enzyme: tyrosinase

Question 7

vitiligo

• clinical finding
• etiology

Answer 7

• local loss of skin pigmentation
• T-cell autoimmune melanocyte destruction

Question 8

how to diagnose vitiligo in light skinned people?

Answer 8

-presence of skin that does not tan in the sun

Question 8

dysplastic nevus syndrome

• what is it
• what mutation

Answer 8

• auto dom disorder
• characterized by formation of dysplastic nevi, may progress to melanoma
• mutation in CDKN2A gene 9p21-11 in 40% of cases

Question 9

albinism

• most common etiology
• 2 main types

Answer 9

• enzyme defect in tyrosinase that makes melanin
  1. ocular
  2. oculocutaneous

Question 9

Ephelis

-etiology

Answer 9

• freckle
• increase number of melanosomes, but not melanocytes

Question 10

solar lentigo

Answer 10

freckles from sun exposure.

-more common in age

Question 12

acquired nevus:

-what are the 3 types, and how do they occur?

Answer 12

1. junctional nevus (most common mole in children)
2. compound nevus
3. intradermal nevus (most common adults)

Melanocytes grow along E-D junction first (junctional), then extend into dermis (compound), then junction melanocytes lost as adult (intradermal)

Question 13

nevus

• what is it
• what to worry about?

Answer 13

• (mole)
• benign neoplasm of melanocytes
• can become melanoma

Question 14

melanoma:

-what is most important risk factor?

Answer 14

sunlight exposure at early age

Question 16

what cell bodies is melanin synthesized in?

Answer 16

melanosomes

Question 17

tuberous sclerosis

-skin clinical features (4)

Answer 17

1. ash leaf macules
2. angiofibromas (‘adenoma sebaceum)
3. shagreen patch (on back, thick leathery skin)
4. periungual fibromas (fleshy tumors around nails)

Question 18

melasma

• what is it
• what associated with

Answer 18

• hyperpigmentation of cheeks
• associated with:
  1. pregnancy
  2. oral contraceptives

Question 19

mongolian spot

Answer 19

• blue butt, congenital birthmark
• results from melanocytes migrating to epidermis but stuck in dermis

Question 20

Melanoma:

4 growth variants: describe them

Answer 20

1. superficial spreading (radial growth, good prognosis)
2. lentigo maligna melanoma (radial growth along E-D junction, good)
3. nodular (early vertical growth causes nodule formation, bad)
4. acral lentiginous–palms, soles and often in dark-skinned people. not associated with UV light