Disorders of Pigmentation and Melanocytes Flashcards
What are melanocytes responsible for and where are they present in the skin?
Skin pigmentation; Basal layer of epidermis
What are melanocytes derived from?
Neural crest cells
How do melanocytes function?
They synthesize melanin in melanosomes using tyrosine as a precursor molecule and pass melanosomes to keratinocytes
What is vitiligo?
Localized loss of skin pigmentation do to autoimmune destruction of melanocytes
What is albinism?
Congenital lack of pigmentation due to enzyme defect that impairs melanin production
What are the two types of albinism?
Ocular and oculocutaneous
What conditions do albinism increase your risk for?
SCC, BCC and melanoma due to UVB
What is another name for a freckle? What is a freckle? What gives freckle its characteristic appearance?
Ephelia; Small tan brown macule that darkens when exposed to light due to increased melanosomes (melanocytes are NOT increased)
What is a melasma? What is melasma associated with?
Mask-like hyperpigmentation of the cheeks associated with pregnancy and oral contraceptives
What is a nevus?
Benign neoplasm of melanocytes associated with hair characterized as a flat macule or raised papule with symmetry, sharp borders, evenly distributed color and small diameter (<6 mm); Nevus can be congenital or acquired
Describe to process of acquired nevus formation
Begin as nest of melanocytes at the dermal-epidermal junction which grows by extension into the dermis. Junctional component eventually lost resulting in an intradermal nevus, which is the most common mole in adults
What can a dysplastic nevus lead to?
Melanoma
What is melanoma?
Malignant neoplasm of melanocytes; MOST common cause of death from skin cancer
What are risk factors for melanoma?
UVB-induced DNA damage, prolonged exposure to sunlight, albinism, xeroderma pigmentosum, dysplastic nevus syndrome (Autosomal dominant disorder characterized by formation of dysplastic nevi)
What are the ABCDs of melanoma?
Asymmetry, Borders irregular, Color not uniform, Diameter >6 mm
What are the two growth phases of melanoma?
1) Radial growth along dermis and superficial epidermis (low risk for metastasis) 2) Vertical growth into the deep dermis resulting in increased risk of metastasis
What is the most important prognostic factor in predicting melanoma prognosis?
Breslow thickness (depth of extension)
What is the most common subtype of melanoma?
Superficial spreading resulting in dominant early radial growth (good prognosis)
What is lentigo maligna melanoma?
Lentiginous proliferation along epidermal-dermal junction (good prognosis)
What is nodular melanoma?
Early vertical growth (poor prognosis)
What is Acral Lentiginous melanoma?
Melanoma arising on pals or soles often in dark-skinned individuals; Not related to UV exposure
