Epidermis and Disorders of Keratinization Flashcards
What are the Lines of Blaschko?
during embyogenesis, karetinocytes migrate from the dorsal neural crest tower the anterior midline of the skin and distally to the extremities in a pattern distinct from dermatomes (dermatomes respect the midline)
What are the four layers of the epidermis?
basal layer, spinous layer, granular layer and cornified layer
Basal layer (stratum basale) is linked to the dermis via what?
hemidesmosomes
In the spinous layer (stratum spinosum) adjacent karatinocytes connect via _____. What immune cells would you expect to see in this layer?
desmosomes, Langerhans cells
_______ are a protein that link desmosomes inter cellularly. (type 1 has higher concentration in upper epidermis and type 3 is located in the basal layer)
Desmogleins (disfunction can lead to pemphigus vulgarism if in the basal layer)
Granular layer (stratum granulosum) is characterized by granules that contain what?
karatohylaline granules (proflaggrin promotes aggregation and stabilization of intermediate filaments in the cornified layer) and lamellar granules (lipids and hydrolyses are released at the stratum corneum to create a hydrophobic barrier)
The cornified layer (stratum corneum) releases ____ ____ ___ like free amino acids, lactic acid or urea that are hygroscopic (retain water)
natural moisturizing factors
Diseases that affect karatinocytes can affect any of the 4 process included in keratinization, which includes: ?
apoptosis, degradation of cellular organelles, formation of lamellar granules and karatohyaline granules (flaggrin-induced keratin filament assembly and cross linking and release of lamellar granules) and enlargement and flattening of karatinocytes
Descquamation occurs through _____ of intercellular bonds via action of hydroslases. Normally keratinocytes shed singly.
hydrolases
What happens when the process of desquamation is altered?
xerosis (dry skin)
How is xerosis characterized and what causes it?
characterized by fine, white scale, hyperkeratosis, sometimes itchy
causes are dehydration of keratinocytes (decrease in NMF or intercellular lipids) or failure to break the intercellular bonds in an organized fashion
What are exogenous and endogenous things that contribute to xerosis?
exogenous: dry climate (forced air), excessive exposure to water (hand washing) and exposure to detergents
endogenous: atopy, ichthyosis vulgarism, renal insufficiency, lipid lowering medications, malnutrition
Hyperplasia of the stratum spinosum is called _____, an increased rate of cell turnover and inflammation, and it can lead to the disease ______.
acanthosis leading to psoriasis
A type of hyperplasia of the stratum corneum is termed ______, abnormal retention of karatinocytes, and it can lead to a disease called ______.
hyperkeratosis leading to keratosis pilaris (accumulation of keratinocytes around the hair follicles)
Hyperplasia in the stratum spinososum and the stratum corneum can be caused by rubbing and scratching which can lead to a condition ____ _____ _____.
lichen simplex chronicus
Describe the “bricks and motor” model of disorders of cornification.
disorders can arise due to karatinocytes cross-linking with intermediate filaments (bricks) or with issues with the intercellular lipids (mortar).
example: lamellar ichtheosis is due to defective keratinization while harlequin ichthyosis is due to a defective lipid barrier
Describe the clinical presentation and associated findings of ichthyosis vulgaris.
ichtyosis vulgarism is the most common disorder of cornification, caused by an autosomal dominant trait with variable expression. clinical presentation is classic “fish scale” appearance. associated findings are asthma, eczema, allergic rhinitis, keratosis pilaris and hyper linear palms
Describe the presentation of keratooderma and its 3 variations.
keratoderma is a family of dominantly inherited diseases characterized by hyperkeratosis, most commonly of he palms and soles (treatments with topical moisturizers and humectants)
subtypes:
diffuse: thick, yellow plaques on plasm/soles, associated with hyperhidrosis
focal: hyperkeratosis over pressure points
punctate: hyperkeratotic papules with a warty appearance
List 3 diseases characterized by altered epidermis.
atopic dermatitis, psoriasis and staphylococcal scalded skin syndrome
Describe the clinical presentation of atopic dermatitis
(aka ezema) an inflammatory disease that includes an aberrant TH2 response (barrier disruption due to a filaggrin defect can predispose patients). patient will complain of pruritic rash that favors flexural surfaces (may lead to secondary infection) and present with irregular erythmatous patches
Describe the clinical presentation of psoriasis.
patient presents with red plaques, thick and adherent scale and nail changes particularly on extensor surfaces which may be itchy or be accompanied by arthralgias (joint pain), an inflammatory disease that is mediated by TH1 and TH17 response causing a faster cell turnover rate
Describe the clinical presentation of staphylococcal scaled skin syndrome.
cutaneous erythema starts at head and generalizes, accompanied by flaccid bullae, desquamation over 3-5 days with extreme skin tenderness/pain and a prodrome of malaise, irritability and fever. caused by staph aureus exotoxin exfoliative toxin a and B that target desmoglein 1 and lead to loss of cell-cell adhesion
**because toxins are renal excreted patients that are younger than 6 yo and patients in renal failure and immunosuppresion have an increased risk for this disease
Where would you culture to support a diagnosis of SSSS
culture of the nasopharynx or conjunctivae or purulent skin lesions, cultures from bullae are negative.
Suggest 5 recommendations for caring for dry skin.
avoid hot showers and prolonged soaking use mild soaps or soapless cleansers avoid products with fragrances pat dry with a towel and apply emollients after bathing use humidifiers during winter months
