Week 2 - B - Psoriasis - H.L.A, Pathogenesis, Precipitants, Presentation/signs, histology, types, treatment Flashcards
What layer of the epidermis is the mitotic pool layer? Where are melanocytes found? What cells make up house dust?
Mitoic pool is the basal layer of the epidermis
Melanocytes are found at the basal layer and above (migrate from neural crest cells)
It is the conreocytes from the keratin layer that are shed from the surface and make up house dust
How do melanocytes produce pigment and what is transferred to?
Melanocytes contain melanosomes which produce pigment by converting tyrosine to melanin pigment.
The melanocytes then transfer the full melanosomes to the keratinocytes via dendritic processes (dendrities)
What are the different cells and fibres found in the dermis? What is the gelatinous amorphous substance of sugar and proteins, that observed in between fibers and between cells in the dermis known as?
Different cells - mainly fibroblasts, macrophages, mast cells, lymphocytes, Langerhan’s cells
Fibres - collagen and elastin
Ground substance is the gelatinous amorphus substance of sugar and proteins observed between the cells and fibres
What makes the ground substance?
Ground substance is transparent, colourless, and fills the spaces between fibres and cells.
It actually consists of large molecules called glycosoaminoglycans (GAGs) which link together to form even larger molecules called proteoglycans.
There are different types of glycosaminoglycans
What are the types of collagen in the dermis?
Type 1 and type 3 collagen
What are the two different layers of the dermis? What are the extensions of dermal connective tissue into the epidermis known as? What are the extensions of the epidermis into the dermis known as?
Papillary dermis is thin and lies just beneath epidermis
Reticular dermis thicker bundles type 1 collagen
Dermal papillae are the protrusions of dermal connective tissue into the epidermal layer.
Rete ridges are the extensions of epidermis into the dermal layer.
Lets discuss some commonly used terms in skin pathology State the meaning of Hyperkeratosis Parakeratosis Acanthosis
Hyperkeratosis - increased thickness of the keratin layer
Parakeratosis - persistnce of nuclei in the keratin layer
Acanthosis - increased thickness of the epithelium
What is papillomatosis and spongiosis?
Papillomatosis is irregular epithelial thickening
Spongiosis is the intracellular oedema of the epidermis
PSORIASIS How common is psoriasis? What is the usual course of the disease?
Psoriasis affects approximately 2% of the population It can affect any age (different clinical variants affect different ages normally)
It is a chronic disease that has a relapsing and remitting course
Exact cause of psoriasis is unknown What is the human leukocyte antigen that is assoicated with psoriasis?
Psoriasis is associated with HLA-Cw6
What is the pathogenesis of psoriasis?
Psoriasis occurs due to two main pathologies
* The hyperproliferation of the epidermal cells - increase in number of cells entering cell cycle from basal layer and faster epidermal turnover
* There is also Tcell driven inflammatory cell infiltration of the dermis and epidermis
What are the different precipitating factors that can cause psoriasis? What infection is strongly linked to the guttate type of psoriasis? What drugs are linked to psoriasis?
* Emotional stress can make it worse
* Infection - streptococcal infetion ie sore throat is strongly linked to guttate psoriasis
* Drugs - beta blockers, lithium, anti-malarias
* Alcohol
* Smoking
What is the rebound phenomenon and what drugs is it seen in for psoriasis?
Sudden cessation of systemic or potent topical corticosteroids can also lead to a severe rebound phenomenon resulting in generalised psoriasis occurring once stopping
Different signs associated with psoriasis - What is Koeber’s phenomenon? - what other conditions is this phenomenon seen in? What is Auspitz sign?
Koeber phenomenon is where psoriasis lesions may develop in sites of trauma 2-6 weeks after the trauma is sustained - eg scratches, burns, surgical trauma - also seen in luchen planus and vitiligo
Auspitz sign is where there is pin point bleeding after successive layers of scale have been removed
What are the different histological features of psoriasis? * Focus on the ones that affect the stratum corneum for now
Stratum corneum - Thickening of the stratum corneum and retention of the nuclei in the stratum corneum - therefore there is hyperkeratosis and parakeratosis
There are also munro microaabscesses - these are small collections of leukocytes within the stratum corneum (complement attracts neutrophils to keratin layer)
Histological features of psoriasis Have mentioned the key ones Hyperkeratosis, parakeratosis and munro microabscesses (collection of neutrophils) in the stratum corneum What are the other histological features in the skin?
There is a thickened stratum spinosum layer and there is large capillary vessels within the papillary dermis
There are many different clinical variants of psoriasis What is the most common clinical variant? What are the key features of this type of psoriasis?
Chronic plaque psoriasis (psoriasis vulgaris - vulgaris means common)
Key features - Symmetrical well defined red plaques with silvery gray scale on extensor aspects of knees, elbows, sacrum and scalp
Auspitz sign - removing scale reveals pin point bleeding
Koebner phenomenon - plaques appear at sites of trauma
What are the nail changes seen in psoriasis?
Onchyolysis - nail separates from the nail bed (gives a white appearance distally)
Nail pitting
Oil-drop lesions
Subungual hyperkeratosis -scaling under the nail due to excessive proliferation of keratinocytes in the nail bed and hyponychium
Nail deformity/dystrophy (wasting away)
The scalps is commonly affected in any of the clinical variants of chronic plque psoriasis What is the presentation of this? Does it affect hair growth?
Scalp psoriasis also presents with the red plques covered with silvery gray scales - it is often itchy
Hair growth is usually unaffected and will grow through the plaque
Guttate psoriasis is a clinical variant of psoriasis Why is it called guttate? What is the presentation of this type of psoriasis? Where are the lesions?
Called guttate as this translates to raindrop - typically the appearance of this type of psoriasis It typically occurs in younger patients about a week after an infection - typically streptococcal sore throat
Multiple lesions appear on the trunk of the patient
Why is guttate psoriasis unlikely to responds solely to topical treatments?
Guttate psoriasis is usually unlikely to respond to topical treatments due to the widespread nature of the condition
Phototherapy is often required
We have spoken about chronic plaque psoriasis usually affects the extensor surfaces Flexor psoriasis can occur and typically affects different areas and the plaques have a different appearance Describe the appearances and what areas are affected?
Flexor psoriasis typically affects the groin, axillae or inframammary areas
The plaques are again red and well demarcated however scale is not a prominent feature as these areas are well moisturized
What is the treatment of flexor psoriasis?
Treatment is usually with a steroid and anti-fungal
Due to potential additional fungal infection
Palmoplantar psoriasis is another clinical variant What is affected in palmoplantar psoriasis? What can develop within the plaques in this case?
Palmoplantar psoriasis affects the palms and soles of feet and is often very painful/disabling
Fissures can develop within the plaques in this case and there is often very thick hyperkeratosis
