Week 2 - H - Pruritus (Pruritoceptive/Neuropathic/genic/Psychogenic), Dermatitis (contact, atopic, seborrhoeic, venous) Flashcards
What is the definition of pruritus?
Pruritus aka itch is defined as
A usually unpleasant, poorly localised, non-adapting sensation that provokes the desire to scratch
There are different classifications for the causes of itch * pruritoceptive * neuropathic * neurogenic * psychogenic Define these classifications of itch and give an example of a condition
* Pruritoceptive itch - something (usually inflammation or dryness) within the skin that triggers itch - eg eczema
* Neuropathic itch - damage to central or peripheral nerves causing itch eg the all over itch some people with multiple sclerosis get or the itch instead of pain some people get following herpes zoster
* Neruogenic itch - no evident damage to nerve tissue but itch caused by CNS effects - eg after opiates
* Psychogenic itch - psychological causes eg itch in delusions of infestation
There are different mediators of itch * Chemical mediators * nerve transmission * central nervous system mediators
What are examples from each of these three?
Chemical mediators eg histamine and tryptase
Nerve transmission mediatiors - unmyelinated C fibres
Central nervous system mediators - opiates
Time to identify different itchy conditions from a picture
Scalp psoriasis -pruritoceptive itch
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This is lichen planus
Pruritic purple planar, poly-angular papules (itchy violaceous flat-topped papules)
Can see the horizontal line showing Koebner’s phenomenon - when lesions arise ina site of trauma
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This patient has a scabies infection
To be exact has Norwegian scabies -the highly infectious chronic crusted form of scabies where thousands of mites embed
Define hypekeratosis, parakeratosis, acanthosis?
* Hyperkeratosis is the increased thickness of the keratin
* Parakeratosis- persistence of nuceli in the keratin layer
* Acanthosis is the increased thickness of the epidermis
What condition discussed in a different set of cards are both hyperkeratosis and parakeratosis seen in?
What else is seen histologically in this condition?
Hyperkeratosis and parakersotis are are seen in the stratum corneum in psoriasis - along wth munro microabscesses (small collections of leucocytes which attract complement causing inflamamtion)
Also there is a thickened stratum spinosum and large capillary vessels within the papillary dermis
What is oedema between keratincoytes known as? - this can occur in eczema
Spongiosis - oedema between keratinocytes
What is another word for dermatitis? - there are many different types
Try and define eczema (not atopic eczema - just eczema in general)
What are the clinical features?
Dermatitis is also known as eczema
Eczema is an inflammatory skin reaction characterized histologically by spongiosus (oedema) with varying degrees of acanthosis
The clinical features are mainly due to the spongiosus
* The main clinical feature is itching - a rash that is never itchy is unlikely to be dermatitis.
* Other features caused by the spongiosus include redness, scaling and papulo-vesicles
Two main classification schemes for eczema are * Time course - acute and chronic * Aetiology based There is an acute phase and a chronic phase in dermatitis
What is seen in acute dermatitis? (histology and clinically)
Acute phase
Definite spongiosus on histology- fluid separating the epidermal cells
ITCH
Papulovesicular rash
Erythematous lesions
Oooze or scaling
What is seen in the chronic phase of dermatits?
Chronic dermatitis
Orthokeratotic hyperkeratotis - thickening of the stratum corneum of the epidermis (hyperkeratosis) with non-nucleated keratinocytes retained in this layer.
(Hyperkeratosis with parakeratosis seen in psoriasis)
Also elevated plaques and scaling
Discussed the acute and subacute symptoms that can occur in eczema There are many different types of eczema and they can be classified as endogenous or exogenous
What is the difference between endogenous and exogenous eczema and give examples?
Endogenous eczema - due to conditions within the body - eg
* atopic dermaitis or
* seborrhoeic dermatitis or
* stasis dermatitis (venous/varicose eczema)
Exogenous eczema - due to external factors * eg contact dermatitis (irritant or allergic)
CONTACT DERMATITIS
The main four types of eczema we shall discuss * Contact dermatitis - exogenous * Atopic dermatitis * Seborrhoeic dermatitis * Stasis dermatitis
What is the difference in the mechanism of irritant and allergic contact dermatitis?
Allergic contact dermatitis is an immune mediated dermatitis due to a delayed (type IV) hypersensitivty reaction to a previously encountered allergen
Irritant contact dermatitis is due to the direct irritant action of a substance on the skin and is common in eg hospital works due to frequent hand washing
What is the immunopathology of allergic contact dermatitis?
In allergic contact dermatitis, the langerhans cells in epidermis process the antigen and present it to the lymph nodes in the dermis containing T-helper cells
The T-helper cells then become sensitised and Th1 mediated reaction happens upon re-exposure to the antigen - typically 24-48 hours after reaction
What are common allergens causing contact dermatitis and what are the symptoms of the condition?
Common allergens include nickel as seen in trouser buckle, jewellery, watches, chromates in cement and leather, susbtances in gloves
Symptoms usually involved a red itchy rash with papulovesicle formation and oozing/crusting (symptoms replicate acute phase of dermatitis)
How do we investigate patients with suspected allergic contact dermatitis?
Gold standard for allergic contact dermatitis is patch testing
Allergens are applied to special chambers and applied to the patients back for 48 hours then removed
Readings are taken at 48 and 96 hours looking for dermatitis-type changes
What is the management of allergic contact dermatitis?
Avoidance of the causative allergen
Regular emollients
Topical steroids
Irritant contact dermatitis as discussed is due to the direct irritant action of a substance on the skin and is not-immune mediated
What are examples of this? What are the symptoms?
Soap/detergent/cleaning products
Water
Oil
Nappy rash - irritant to urine
Symptoms include erythema, pupulovesicular rash + ozzing/crusting
Difficult to distinguish from allergic contact dermatitis based on clinical features alone
What can occur in both irritant and allergic contact dermatitis if prolonged untreated exposure?
The eyrthema and papulovesicles can lead to eventual lichenification (thickening of the skin) and fissuring
What is the management of irritant contact dermatitis? What may irritant contact dermaittis often overlap with?
Avoidance of irritants
Use soap substitutes eg dermol 500
Regular emollients
Topical steroids for flare-ups
May overlap with atopic dermatitis
ATOPIC DERMATITIS
Multifactorial cause - genetic and environmental factors resulting in inflammation
What other conditions is eczema commonly linked to?
The atopic triad aka the atopic March
* Atopic eczema - usually begins in infancy
* Asthma - usually after 2 years old
* Allergic rhinitis - hayfever - usually later in late child / teen years
Atopic eczema is the most common inflammatory skin disease in children
Where does the conditions often start in children vs in older children?
In children, it often starts on the face and extensor surfaces
In older children, it starts in the typical flexural pattern (ante-cubital fossa, popliteal fossa and flexor aspect of wrists)
The diagnosis of eczema is a clinical one The diagnostic criteria comes from the symptoms
What is the diagnostic criteria?
ITCH + 3 or more
* Visible flexural rash
* History of flexural rash
* Dry skin
* Onset at less than 2 years old
* Personal history of atopy or first degree relative
* Rash on cheeks and extensor surfaces in infant
How would describe the acute lesions as seen in atopic eczema?
Erythematous pruritic rash indicating inflammation
Can also cause the small vesicular rash that oozes and may crust increasing likelihood of pathogenic skin infection
Chronic in scratching in atopic eczema can cause different signs What are these?
Excoriations may be seen - scratch marks
Lichenification may occur - exaggeration of normal skin creases caused by thickened skin due to chronic scratching
Also habit scratching
Secondary infection
Atopic eczema can affect both the child (keeping awake at night) and the parents (having to wake a night due to child)
Secondary infection in eczema is common What would indicate this? What is the common pathogen? What is the treatment?
Secondary infection would be indicated by crusting of the skin
Usually caused by a staph aureus infection
Treatment is usually topical fusidic acid or oral flucloxacillin
What is the infection known as when the herpes simplex virus affects previous areas of eczema? How are the lesions described here?
This is known as eczema herpeticum
Rememeber monomoprhic punched-out lesions
Mutation in which gene increases the likelihood of atopy? What is the purpose of this gene?
Mutations in the filaggrin gene are linked to an increase in atopy (atopic eczema, asthma and hayfever)
Filaggrin is a protein found in the granaular layer of the epidermis and is very important in helping the terminal differentation of the keratinocytes
This is allows the stratum corneum to form which is the main outer cutaneous barrier
If there is a mutation in the filagrin gene preventing terminal differentiation of the keratinocytes therefore impairing the function of the stratum corneum, how can this cause eczema?
Normal barrier function
* Prevents water loss - therefore impaired function results in dry skin
* Prevents entry of infectious agents, irritants and allergens - impaired function results in likelihood of eczema
What is the allergic response that causes the IgE production as seen in atopic individuals?
Atopic individuals may have overactive Th2 lymphocytes which releases different inflammatory cytokines
IL-4 released from TH2 cells causing B cell maturation into IgE cells
What tests can be done to test for immediate hypersensitivityes that are linked to eczema? (eg due to food allergic or latex allergy) What type of hypersensitivty is atopic eczema?
Tests for immediate hypersensitivity (type 1) is usually skin prick testing followed by RAST (radioallergosorbent testing) testing if skin prick fails
Atopic eczema is type IV hypersensitivity reaction - T cell mediated
What is the management of eczema?
Cotton clothes and bedding
Emollients (moisturisers) used at least twice a day are advised to prevent drying and itchy of the skin
Daily steroids for active sites
- * Hydrocortisone 1% for mild eczema
- * Clobetasone butyrate 0.05% for moderate (eumovate)
- * Bethametasone valerate 0.1% for severe (betnovate)
- * Clobetasol proprionate 0.05% for very severe (dermovate)
If the emollients and steroids fail to treat eczema What is second line therapy? - paritcularly used if having to use potent/very potent sterois for prolonged periods of time
Calcineurin inhibitors eg tacrolimus
Phototherapy - mainly UVB or immunosuppresants are usually last line options given by dermatologists
What is seborrhoeic dermatitis? How does it present? (where is affected) What causes it?
Seborrhoeic dermaitits is a common long-term skin disorder affecting areas of the sin that are rich in sebaceous glands
Typically causes red, scaly rash affecting the scalp (dandruff), eyebrows, nasolabial folds, cheeks and flexures
It is caused by the overgrowth of skin yeasts (eg malassezia)
What is the treatment of seborrhoeic dermatitis?
Mild topical steroid creams/antifunggals are usually given to treat seborrhoeic dermatitis eg daktacort (hydrocortisone and miconaole) or ketaconazole
What is one of the common causes of severe seborrhoeic dermatitis presentations?
HIV
What is venous dermatitis also known as? Who does it typically present in?
Venous dermatitis aka stasis eczema aka varicose eczema
Typically occurs in patients with a chronic venous insufficiency
What is the presentation of venous eczema and why does chronic venous insufficiency cause it?
Chronic venous insufficiency causes an increase in hyrodstatic pressure (pressure pushing out of the veins) causing the vens to leak causing oedema
This can lead to the dry, flaky and itchy skin seen in venous eczema
Photosensitive eczema is a condition where a subject’s skin becomes inflamed due to a reaction to sunlight or artificial light. What is this also known as? What is the typical feature where the eczema stops known as?
Photosensitive eczema is also known as chronic actinic dermatitis aka photodermatitis
There is a typical ccut-off at the patients collar as this is not exposed to the sunlight
