Melanocytes and Disorders of Pigmentation Flashcards
what are melanocytes?
cells derived from the neural crest, reside in the basal layer of the epidermis, and are responsible for producing pigment (melanin). density of melanocytes varies by location and degree of sun-damage normal, sun-protected skin on the trunk: ratio of melanocytes to keratinocytes is roughly 1:10
what type of cell is a melanocyte? what does it transfer and how?
dendritic cell, whose dendrites extend long distances allowing it to make contact with multiple keratinocytes and transfer melanosomes.
increased pigmentation causes?
degreased?
loss of pigment?
hyperpigmentation.
hypopigmentation.
depigmentation.
(use a woods light: depigmented = enhanced by light)
autoimmune disorder resulting in depigmented patches?
vitiligo. destruction of melanocytes: fewer or none. symmetric involvement, with facial (particularly periorificial), hands, feet, ankles, knees, and elbows being the most frequent sites affected. unpredictable course, spontaneous repigmentation can occur.
vitiligo treatment?
Topical corticosteroids are used first-line. For extensive or recalcitrant disease, ultraviolet phototherapy may help stimulate repigmentation.
inherited genetic disorder that results in congenital absence or marked reduction of pigment in the skin, hair, and eyes?
oculocutaneous albinism. occurs as the result of defects in melanin production. diffuse involvement of skin and hair. visual symptoms (e.g. decreased visual acuity, nystagmus) are common. high risk for skin cancer.
benign proliferations of melanocytes? types?
melanocytic nevi. 3 types: junctional, compound, intradermal
types of nevi/distinctions?
junctional nevi have nests along the dermal-epidermal junction; compound have nests along the DEJ and in the dermis; intradermal nevi have nested melanocytes within the dermis. w maturation: evolution from a junctional nevus to compound nevus to intradermal nevus. distinctions are difficult to make clinically, although junctional nevi are typically flat (“young nevi”) and intradermal nevi raised (“old nevi”).
congenital melanocytic nevi?
larger, 1 cm to greater than 20 cm. present at birth. distress. higher risk of melanoma.
acronym for nevus evaluation?
ABCDE. A=asymmetry B=border irregularity/blurred border C=color heterogeneity D=diameter >6mm (does not apply to congenital melanocytic nevi) E=Evolution or change
small 1-3 cm lesions?
ephelides. sun-exposed pts. darken w sun exposure. marker of UV-induced damage, risk factor for melanoma
well-circumscribed uniformly light to dark brown macules or patches which typically appear in infancy or early childhood?
CALM. multiple are rare, may be sign of neurofibromatosis
what is a solar lentigo?
tan to dark brown or black macule due to exposure to UV irradiation. seen later in life and are often bigger, ranging in size from 5- 15 mm in size. occur in sites of chronic sun exposure, and may darken with sun exposure.
blue-gray patches over the lumbosacral region of infants with darker skin types?
dermal melanocytosis. pigment typically fades with age. blue color secondary to melanocytes in the middle to lower dermis (deeper than brown lesions). lesions in other locations have persistence over time and tend to be larger (few cm or more), which can help distinguish them from blue nevi.
what is neurofibromatosis type I?
autosomal dominant genetic disorder caused by mutations in the NF1 gene encoding neurofibromin. multiple café-au-lait macules in childhood. Axillary and inguinal freckling. later neurofibromas can develop within the skin- soft or rubbery papules. Plexiform neurofibromas = larger plaques w “bag of worms” feel in the skin
