Pathology of rashes Flashcards
What is hyperkeratosis?
Increased thickness of keratin layer
What is parakeratosis?
Persistence of nuclei in the keratin layer
What is acanthosis?
Increased thickness of the epidermis
What is papillomatosis?
Irregular epithelial thickening
What are the four main reaction patterns in rashes?
Spongiotic
Psoriasiform
Lichenoid
Vesiculobullous
Which condition is an example of a spongiotic rash?
Eczema
Which condition is an example of a psoriasiform rash?
Psoriasis
Which conditions are examples of a lichenoid rash?
Lichen planus
Lupus
Which conditions are examples of a vesiculobullous rash?
Pemphigoid
Pemphigus
Dermatitis herpetiformis
What is a spongiotic rash pattern?
Intraepidermal oedema
What can be seen histologically in a psoriasiform rash?
Elongation of the rete ridges
What can be seen histologically in a lichenoid rash?
Basal layer damage
What can be seen histologically in a vesiculobullous rash?
Blistering
What is the Koebner phenomenon?
A new psoriatic lesion may appear at site of trauma
What is the pathological process in psoriasis?
Epidermal hyperplasia - keratin migrates from the basal layer to the keratin layer much faster than normal
There is increased epidermal turnover which causes scaly plaques to form on the skin
Which sites are most commonly affected by psoriasis?
Extensors (elbow, knee) Scalp Sacrum Hands Feet Trunk Nails
What do the plaques in psoriasis look like?
Symmetrical
Well demarcated
Erythematous
Scaly
What are some of the nail changes that can occur in psoriasis?
Onycholysis
Nail pitting
Dystrophy
Subungal hyperkeratosis
What is acne vulgaris?
A chronic inflammatory disease of the pilosebaceous unit
Where is acne vulgaris typically distributed?
Face
Upper back
Anterior chest
At what age do patients typically present with acne vulgaris?
14 -17 years in females
16 -19 years in males
What is the pathogenesis of acne vulgaris?
There is plugging of the pore by sebum
Bacterial colonisation of the pore occurs, and fills with keratin and sebum creating comedones (whiteheads and blackheads)
These rupture, causing inflammation
What is acne rosacea?
Prominent facial flushing exacerbated by sudden change in temperature, alcohol or spicy food
A rash consisting of papules, pustules and erythema but no comedones
Where is acne rosacea distributed?
Nose
Cheeks
Chin
Forehead
What are immunobullous diseases?
Skin diseases/rashes that have blisters as the primary feature
Which patients are typically affected by bullous pemphigoid?
Elderly patients
What does the blister in bullous pemphigoid look like?
Large tense bullae on normal skin or erythematous base
What is the pathology in bullous pemphigoid?
Splitting at the DEJ - pemphigoiD splits Deep at the DEJ
Circulating IgG antibodies attack the anchors that hold the basal cells to the basement membrane
Which areas does bullous pemphigoid tend to affect?
Either localised to one area or widespread over proximal limbs and trunk
What is pemphigus?
A rare autoimmune bullous disease resulting in loss of integrity of epidermal cell adhesion
What is the most common form of pemphigus?
Pemphigus vulgaris
What is the pathogenesis of pemphigus vulgaris?
IgG auto-antibodies made against desmoglein 3 which maintains desmosomal attachments
Immune complexes form on cell surface, and there is complement activation and protease release causing disruption of desmosomes
This causes acantholysis
Which areas does pemphigus vulgaris tend to affect?
Face Axillae Scalp Groin Trunk Mucosal tissue e.g. eyes, genitals, mouth, respiratory tract
In which cases might pemphigus vulgaris be fatal?
Extensive involvement of mucosal tissue e.g. respiratory tract
What is Nikolsky sign?
A skin finding in which the top layers of the skin slip away from the lower layers when slightly rubbed
Is Nikolsky sign positive or negative in bullous pemphigoid?
Negative
Is Nikolsky sign positive or negative in pemphigus?
Positive
What do the lesions in pemphigus vulgaris look like?
Flaccid vesicles/bullae – thin roofed
Lesions rupture to leave raw areas
Erosions rather than bullae
What is the prognosis following diagnosis of an immunobullous disease?
Chronic self limiting condition: most patients achieve remission after 3-6 months
High mortality if left untreated
Which immunobullous disease has a strong association with coeliacs disease?
Dermatitis herpeteformis
Which gene is dermatitis herpeteformis associated with?
HLA-DQ2 haplotype
What are the lesions in dermatitis herpeteformis?
Intensely itchy symmetrical lesions, often excoriated
Papillary dermal microabscesses
Where are the lesions in dermatitis herpeteformis typically found?
Elbows
Knees
Buttocks
