1.4 Disorders of Pigmentation and Melanocytes Flashcards
what are melanocytes derived from?
neural crest
how to distinguish nevus from melanoma?
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
neurofibromatosis 1
-skin findings (3)
- cafe au lait spots
- axillary/inguinal freckling
- neurofibromas
melanoma
- what is it
- how does it progress?
- 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)
Tuberous sclerosis
-what is it
- auto dom disorder
- causes benign tumors of many organs (brain, eyes, heart, kidney, skin, lungs)
chemical production of melanin (simplified)
tyrosine –> melanin
important enzyme: tyrosinase
vitiligo
- clinical finding
- etiology
- local loss of skin pigmentation
- T-cell autoimmune melanocyte destruction
how to diagnose vitiligo in light skinned people?
-presence of skin that does not tan in the sun
dysplastic nevus syndrome
- what is it
- what mutation
- auto dom disorder
- characterized by formation of dysplastic nevi, may progress to melanoma
- mutation in CDKN2A gene 9p21-11 in 40% of cases
albinism
- most common etiology
- 2 main types
- enzyme defect in tyrosinase that makes melanin
1. ocular
2. oculocutaneous
Ephelis
-etiology
- freckle
- increase number of melanosomes, but not melanocytes
solar lentigo
freckles from sun exposure.
-more common in age
acquired nevus:
-what are the 3 types, and how do they occur?
- junctional nevus (most common mole in children)
- compound nevus
- 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)
nevus
- what is it
- what to worry about?
- (mole)
- benign neoplasm of melanocytes
- can become melanoma
melanoma:
-what is most important risk factor?
sunlight exposure at early age
what cell bodies is melanin synthesized in?
melanosomes
tuberous sclerosis
-skin clinical features (4)
- ash leaf macules
- angiofibromas (‘adenoma sebaceum)
- shagreen patch (on back, thick leathery skin)
- periungual fibromas (fleshy tumors around nails)
melasma
- what is it
- what associated with
- hyperpigmentation of cheeks
- associated with:
1. pregnancy
2. oral contraceptives
mongolian spot
- blue butt, congenital birthmark
- results from melanocytes migrating to epidermis but stuck in dermis
Melanoma:
4 growth variants: describe them
- superficial spreading (radial growth, good prognosis)
- lentigo maligna melanoma (radial growth along E-D junction, good)
- nodular (early vertical growth causes nodule formation, bad)
- acral lentiginous–palms, soles and often in dark-skinned people. not associated with UV light
