Melanocytic Lesions Flashcards
what gene determines the balance of pigment in skin and hair?
melanocortin 1 receptor gene
eumelanin hair colour
any colour apart from red
phaeomelanin hair colour
red hair
role of the MC1R
turns phaeomelanin into eumelanin
what does one defective copy of MC1R cause?
freckling
what does two defective copies of MC1R cause?
red hair
freckles
define freckles (ephilides)
patchy increase in melanin pigmentation (reflects clumpy distribution in melanocytes)
what causes more freckles occur
UV exposure
does pale skin have fewer melanocytes?
yes
what are actinic lentigines
age or liver spot
what are actinic lentigines related to?
UV exposure
where are actinic lentigines common?
face
forearms
dorsal hands
define melanocytic naevi
moles
define congenital melanocytic naevi
birthmark
if large there is risk of developing into melanoma
describe usual type acquired naevi
melanocyte keratinocyte ratio breaks down
benign lesions
stages in naevus development
junctional naevus= cluster at DEJ
compound naevus= dermis (migrate down skin) and moles elevate as they mature
intradermal naevus= entirely dermal
appearance of dysplastic naevi
above 6mm in diameter variegated pigment border asymmetry atypical architecture host reaction involving fibrosis and inflammation
two ways a dysplastic naevi can develop
sporadic
familial
three examples of rare naevi
halo naevi
blue naevi
spitz naevi
describe spitz naevus
under 20 years
large spindle and/or epitheloid cells
pink colouration due to vascularisation
(malignant variant called spitzoid)
