Baseline skin color without sun exposure
Facultative skin color
skin color after secondary melanin induction.
What accounts for differences in skin color?
Tyrosinase activity and subsequently the amount of melanin in the skin. Melanosomes are larger, and there are more.
Pigmentary demarcation lines
Abrupt transitions between lighter ventral and darker dorsal skin that may be photosensitive. Aka as Voight's or Futcher's lines
Characteristics of normally pigmented guns
common in dark sin, seen in gingiva, hard palate, buccal mucosa. Symmetric, evenly pigmented.
What is a dermal melanocytoses
a blue hue in the skin due to melanocytes that are located in the dermis. `
Congenital dermal melanocytosis
a dermal melanocytosis which appears as a benign, flat, birthmark which may have way borders or irregular shape. Most common in asians, resolves during childhood.
Nevus of ota
congenital dermal melanocytoses common in aisians and blacks that are found in first 2 branches of trigeminal nerve, often unilateral, seen in sclera.
Nevus of ito
Dermal melanocytoses in the scapular, or posterior supraclavicular nerve distribution.
pigmented band of nail plate because of increased melanin by melanocytes in nail matrix. Can darken with age. Look for symmetry and presence on multiple nails to rule as benign.
Punctate keratosis of palmar creases
Autosomal dominant, hyperkaratotic plugs in pam creases, appear during adolesence, aggrevated by manual work. dDx from warts.
How does eczema present in darker (vs lighter) skin
erythema not seen, xerosis, follicular prominence, distribution same. Both have scale, excoriations, and treated the same.
Seborrheic dermatitis presentation in lighter skin.
Sharply demarcated pink patches with yellow-white scaling in areas of high sebum production.
Seborrheic dermatitis in darker skin
erythema is not present, +/- scaling, pigmentary change may be only detectable change (lighter or darker).
Folliculitis presentation in darker skin.
Erythema hidden, hyperpigmented macules only.
Dermatomyositis presentation in darker skin
Top Dx in darker skin
acne, dyschromia, contact derm/ezcema, seborrheic dermatitis.
Acne in pigmented skin
occurs at same rates in all skin types, but darker skin have less nodulocystic acne, more hyperpigmented macules, and higher incidence of keloidal acne.
Curved hair follicle reenters skin, foreign body reaction-->swelling and erythematous pustules/papules.
Subsequent shaving traumatizes papules, keloids can eventuially form.
chronic, progressive, keloidal scarring of the nape of neck.
Follicular inflammation->follicle rupture->foreign body rxn->keloids->alopecia.
Best to grow out hair, use Ab, intralesional steroids, surgery.
Dermatosis papulosa nigra
multiple pigmented macules on face and neck, 35% black patients, start in adolesence increase with time. In malar region and temples. Represent tiny seborrheic keratoses
Benign, symmetric facial hyperpigmentation esp in women. Genetic, hormonal, UV, and radiation causes. Can develop during pregnancy
multiple, hypopigmented, ill-defined scaly pathces. May be a variant of PIG after eczema. Resolves in adolesence bc of increased sebum production. Tx with emollients, mild topical steroids.
Gene associated with 50% of psoriasis patients
PSORS1, a HLA-Cw6 gene. Confers increased risk and associated with early onset and guttate psoriasis.
What kind of immune cells are abundant in psoriasis lesions?
CD4+ helper T cells, especially Th17 cells.
WHich cytokine produced by Th17 cells is associated with T cell influx in psoriasis
WHich cytokine produced by Th17 cells is associated with acanthosis
Anti-IL23 antibody that inhibits T cell differentiation to Th17
Role of TNF alpha in psoriasis
Pro-inflammatory, derived from T cells, keratinocytes, dendritic cells,
Tx of Psoriasis if involved to only 10-20% of skin surface
topical steroids and vitamin D analogs
Tx of psoriasis if 10-20% of body surface
UV phototherapy, retinoids, methotrexate, cyclosporin
3 FDA approved drugs to target TNF alpha in psoriasis
enteracept, infliximab, adalimumab
Th1 associated cytokines
IFN gamma, IL-12, IL-2
Th2 associated cytokines
IL-4, IL-5, IL-10
Th17 associated cytokines
IL-23, IL-17, IL-22