Infammatory dermatoses Flashcards
(10 cards)
Dsercibe the structure of the dermis and the arrangement of dermis and epidermis.
The epidermis sits on top of the dermis (in between the epidermis and dermis is the basement membrane).
The dermis contains the adnexal structures – pilosebaceous unit (hair follicle, sebaceous gland and arrector pili muscle) and sweat glands – eccrine (make watery sweat – distributed all over the body) and apocrine (make a viscous sweat – distributed on axillae and groin) glands.
The dermal matrix is made up of collagen, elastin, GAGs, blood vessels and nerves.
Describe some of the cells
Melanocytes on basement membrane: produce melanin and protect keratinocyte nuclei
Langerhans cells = APCs within epidermis
Merkel on basement membrane - involved in sensation
Keratinocytes - Anucleuar stratified cells form barrier
What are the layers of skin from deep to superficial?
stratum basale,
stratum spinosum,
stratum granulosum,
stratum corneum
Describe the passage of keratinocytes through the epidermis
Keratinocytes begin at the bottom in the stratum basale
Proliferate – as they move up epidermis, differentiate to produce keratohyalin granules
Form keratin, which makes up the bulk of the stratum corneum. Once cells have reached the corneum, they lose their nuclei and form a dead layer – BARRIER
Describe the barrier function of keratinocytes in the stratum corneum
The keratinocytes are like bricks – in between them, lipids and proteins (one of which is filagrin) form cement. Together, they form a tight seal (protective against irritants, allergens and organisms).
If this system is defective, in can lead to eczema and dry skin. A mutation in the filagrin gene is common in eczema patients.
Describe Atopic eczema
The barrier of the skin may defective (e.g. due to a filagrin gene mutation → dryness), certain insults can occur. Allergens can penetrate → sensitisation.
Allergens include pollen, house dust mites and food products.
Irritants an also penetrate (e.g. soap, detergents), drying out the skin further and make the barrier function even more defective. Pathogens can also infiltrate (e.g. S. aureus) the skin.
The immune response is activated via the Langerhans cells → acute atopic dermatitis, with activation of CD4
lymphocytes (Th2 response). If this is left to go on for weeks/months, this can turn into a chronic atopic eczema, which shows more of a Th1 immune response.
Describe the atopic march
Atopic diseases come about at different times in an individual’s life. The first disease to come on is eczema, then food allergies, then asthma, and then rhinitis. An individual may only get one of these, but GENERALLY, it happens in this order.
The underlying problem is the dry skin and defective barrier function of the skin. The defective barrier function in eczema can lead to sensitisation.
What is a sign of filagrin gene mutation?
PALMAR HYPERLINEARITY – many lines on the hand. 5-10% of the population has this
What is a theory regarding the development of childhood food allergy?
There is a theory that, if a baby is exposed to allergens on their skin (but not sufficiently in their gut), they are
more likely to develop sensitivity. Whereas, if they have adequate oral intake, this will be protective against
sensitisation of the food allergy.
What are the common locations for eczema outbreaks?
As the child grows up, the pattern of the eczema often changes. It remains on the face, but as the child gets older, it particularly affects the antecubital fossa, the popliteal fossa, hands, face and neck (flexural areas, and areas where there is build up of sweat).
