Dermatology Flashcards
What rash is associated with coeliac disease
dermatitis herpeticum
Describe dermatitis herpeticum rash
Pruritic papulovesicular rash affecting both elbows and back
Underlying mechanism of keloid scars
Excess collagen production (fibroblast)
What is a keloid scar
Raised thickened area at site of previous skin injury
Histology of alopecia
T cells within peribulbar infiltration that release cytokines and chemokines -> reject hair -> hair loss
Aeitology of tuberous sclerosis
mutations of TSC1 gene on chromosome 9 or TSC2 gene on chromosome 16 (most common)
50% autosomal dominant
50% sporadic
What does TSC1 gene code for?
hamartin
What does TSC2 gene code for
tuberin
Pathophysiology of tuberous sclerosis
Hamartin and tuberin form a regulatory complex that acts to limit the activity of rapamycin complex 1
Mutations here lead to poorly controlled cell growth
Clinical presentation of tuberous sclerosis
Epilepsy
Learning disability
Hypomelanotic macules, ash-leaf macules, shagreen patches, adenoma seabeecum
Eyes -retinal hamartomas
Cardiac rhabomyomas
Investigations
Wood light
Risk factors for psoarsis
Positive family history
Genetics - guttate psoarsis ass. with HLA-BW17, HLA-BLA13, HLA-C6
Infection
Sunlight
What is Koebnar phenomen
psoarsis occurring on pervious areas of trauma
Pathophysiology of psoarasis
T cell immune-mediated autoimmune disorder
T helper cells produce inflammatory cytokines - inc. interlukin-IL 17 AND IL 22 and tumour necrosis factor
These stimulate proliferation of. keratinocytes and production of dermal antigen adhesion molecule in local blood vessels -> stimulates cytokine release
Increases skin cell turnover - immature skin cells migrate to surface with dead skin cells remaining ->. plaque lesions
Typical tinea corporis lesions
annular, erythamatous, scaly pruritic border with clear centre
How does Cypoterone acetate work?
Inhibits 17-alpha - hydroxylase
How is erythema multiform characterised?
target lesion
What is. erythema multiform pmost commonly precipitated from?
Herpes simplex virus
Mycoplasma pneumonia
Describe target lesions
concentric rings, colour variation, symmetrical
Name the two layers of the skin
Epidermis
Dermis
Epidermal development
Surface ectoderm covers the developing embryo (single-layered epithelium)
Proliferated to surface epithelium, periderm
When does keratinisation occur?
19 weeks - skin becomes impermeable
Where are melanocytes derived from
ectoderm
they migrate from neural tube to epidermis
Non-functioning until 2nd trimester
Pathophysiology of congenital dermal melanocytosis
Melanocytes fail to reach their proper location in epidermis and entrapped in dermis at time of birth
Birthmark slowly resolves with time
Dermal development
Face and anterior scalp are dried from neural crest ectoderm
Extremities and trunk from mesoderm
When are dermal. fibroblasts developed by?
6- 8 weeks
When do the fibroblast synthesise collagens and micro fibrillar components
12- 15 weeks
What are the layers of the epidermis
stratum corner - outer layer of dead cells and keratin
stratum lucid (only on palm and soles)
Stratum granulosum
Stratum spinosum
Stratum basale
What type of cells is epidermis
stratified squamous epithelium
Name the cell types of epidermis
Kertainocytes
Melanocytes
Merkel cells
Langerhans cells
