Pigmentation - physio, disorders, pigmented lesions Flashcards
What is melanin and its function
- Pigmented polymer
- protects DNA from UV radiation (200-2400nm)
- deactivates free radicals
What are the 3 types of melanin, location and production
- Eumelanin (hair/skin)
- Tyrosine ->(Tyrosinase) ->Eu-M
- Pheomelanin (blond/red hair)
- Tyrosine+cysteine ->(Tyrosinase) - >Pheo-M
- Neuromelanin (Neural tissue)
- unclear fx/production
How/Where is melanin made and distributed?
In melanocyte
- melanin in made in ER, packed in Gogi and released into melanomsome
- Melanosome is distributed to keratinocyte via dendritic processes of melanocyte
In keratinocyte
- melanosome is phagocytized into keratinocyte, and incorproated to cell membrane surrounding nuclei
What are melanocytes, embryology, location in the body
Melanocytes are spindle cells that produce melanin
- derived form neural crest cells in 10th wk GA
- migrate to epidermis (s. basale), hair follicle, mucous membrane, dermis (then named nevus cells), neural tissue, eye, inner ear
What is a nevus cell - and how does it differ from melanocyte?
- Nevus cell is a melanocyte whic hhas migrated into dermis
- Differs from melanocyte in that the nevus cell is:
- round/spindle (vs. dendritic)
- located in dermis (vs. s. basale)
- lives in clusters (vs. individual)
- Similar to melanocyte in that the nevus cell
- has small nuclei
- mitoses are rare
What 4 pigments are responsible for skin color? (list chromophore)
- Endogenous (melanocytes)->Brown w melanin
- Exogenous (diet) ->Yellow/orange w carotene
- Intravascular-> Blue w deoxyhemoglbin
- Intravascular ->Red w oxyhemoglobin
What determines the skin pigment at baseline?
- Density of melanosomes in the keratinocyte and the density of melanin in each melanosome
- Balance of Eumelanin (brown-blakc) vs Pheomelanin (yellow-red)
What factors control the color of skin
- Genetics
- Hormonal control
- melanotrophic hormones (MSH, ACTH, pregnancy, lipotropin)
- UV - stimulates release of melanotrophics from keratinocytes which stimualtes melanocytes to produce more melanin
What are hypopigmentary disorders
- Vitiligo
- Albinism
- Waardenburg
- Leptomeningeal melanocytosis
- Neurocutaneous melanosis
What is vitiligo
Hypopigment disorder with selective destruction of melnocytes in epidermis +/- follicles
- Onset 10-30yo, progressive
- sharply demarcated hypopigment macule which coalesce
Treatment
Non-op: Repigment with phototherapy, Depigment with hydroquinone, Tattoo
Operative: punch graft
What is albinism
Congenital hypopigmentary disorder - no production of melanin
- Onset birth
- No pigment in hair, eyes, skin
- normal density of melanocytes
List types of Nevocellular Nevi
Acquired
- Junctional nevus - at D-E jx
- Compund nevus - in dermis and epidermis
- Dermal nevus - in dermis only
Congenital
- GCMN
- Non-giant CMN
Special
- Halo nevus
- Spitz nevus
- Atypical nevus
When do acquired nevocellular nevi appear, change with age?
- Not present at birth
- progress from junctional ->compound ->dermal
What is a giant CMN?
- Pigmented nevus present at birth or shortly therafter, caused by abnormal migration of melanoblasts b/w 8-24th wk GA
- link to c-met oncogene
How is GCMN defined clinically
>20cm dimater
50% of body region
What conditions are associated w GCMN
- leptomeningeal melanocytosis
- NF
What are treatment options for GCMN?
Medical
- observe (dermoscopy/photo)
- Laser
- dermabrasion
- chemical peel
Surgical
- Serial excision, Tissue expansion, local flaps
What is the prognosis of GCMN
- <4% malignant transformation , usually <age>
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If child presents w GCMN, what are RFs for associated neurocutaneous melanosis
- GCMN on midline trunk/calvarium
- seizures, abnormal CNS development
- multiple satellite lesions
Workup for? neurocutaneous melanosis
MRI <6mths of age
What is a halo nevus?
Pigmented nevus w area of surrounding hypopigment
Treatment - expectant, excise if risk dysplastic nevus
