B109 Acute inflammatory dermatoses

Question 1

List the acute inflammatory dermatoses

Answer 1

Utricaria

Acute eczematous dermatitis

Erythema multiforme

Question 2

Describe urtricaria, presentation and molecular mechanism

Answer 2

Hives or wheals: flate, raised edematous pruritic plaques

• Caused by localized tissue mast cell degranulation.
• Can be IgE mediated, or can be directly stimulated by certain drugs: opiates, some antibiotics.
• In most cases the cause of degranulation is not clear.

Histology:

• sparse/mild perivenular mononuclear cell infiltrate and sometimes eosinophils. neutrophils are rare.
• The edema causes more loose distribution fo the collagen bundles.

Presentation.

• Typcially affects people between 20 and 40, but also children and elderly
• The lesions can last for hours or even days and weeks.
• Persistent lesions are often due to urticarialvasculitis, due to complement deposition in the dermal venules or a subtype without complement deposition that is idiopathic but sill inflames the venules.
• It does not cause significant symptoms, aside from the itching, and the embarrasing rash.

Treatment:

• Antihistamines
• Systemic steroids in severe cases

Question 3

Type os Acute eczematous dermatitis,

Answer 3

Eczema: term to describe skin lesions that form pruritic red papules, vesicles, which rupture and ooze, and become a crusted skin rash

Allergic contact dermatitis: name

Atopic dermatitis: Thought to be caused by defects in keratinocyte barrier function, genetic basis probably.

Drug related eczematous dermatitis: hypersensitivity drug reaction

Photoeczematous dermatitis: Occurs as an abnormal reaction to UV or visible light.

Primary irritant dermatits: From skin damage, chemical, physical

Question 4

Histology of acute eczematous dermatitis

Answer 4

Epidermal edema or Spongiosis is a key feature, and acute eczematous dermatitis is also called Spongiotic dermatitis

Mast cell degranulation stimulates edema

Epidermal cells become swollen and stretches the intercellular attachments which break, causing scaling.

Perivascular lymphocyte infiltration occurs

and eosinophils may also be present, especially in drug induced eczematous dermatitis reactions.

Question 5

Clinical symptoms and consequences of eczematous dermatitis

Answer 5

Itching.

Chronic/repeated expsoure results in epidermal thickening and scaling - acanthosis and hyperkeratosis.

chronic itching may result in formation of Lichen Simplex Chronicus, rough scaly skin that results from epidermal scarring and resembles the lichen on a tree.

Question 6

What is the ‘atopic triad’

Answer 6

Atopic dermatitis

Atopic asthma

Allergic Rhinitis

Which frequently present together.

Question 7

Erythema multiforme causes

Answer 7

An uncommon hypersensitivity reaction to certain infections and certain drugs.

Herpes simplex, Mycoplasma

Sulfonamies, penicillins, salicylates, antimalarials.

Question 8

Erythema multiforme morphology and histology

Answer 8

Morphology:

• Various lesions, hence multiforme. Macules, papules, vesicles, bullae, and targetoid lesions of red macules or papules with a more pale center.

Histology:

• Results from Cytotoxic T cells attacking the basal cells of the skin or mucosae, which display cross-reacting antigens to the drug or microbe.
• Perivascular lymphocytes and lymphocytes along the border of the dermis-epidermis junction.
• Zones of basal epidermal necrosis and blister formation as the epidermis lifts lifts off.
• Severe forms the necrosis goes through all layers, called toxic epidermal necrolysis

Question 9

Erythema multiforme symptoms and clinical

Answer 9

Like its various types of lesions, it has broad range of severities.

Infectious forms are less severe

Drug induced forms are worse and the rare risk of progressing to lethal types, Stevens-Johnson’s syndrome of toxic epidermal necrolysis. The cause of this severe reaction is idiopathic.

Question 10

List the chronic inflammatory dermatoses

Answer 10

Psoriasis

Lichen planus

Lichen simplex chronicus

Question 11

Psoriasis morphology and histology

Answer 11

Morphology

• Well-demarcated, large raised plaques, covered by a white/silverish scaly flaky epidermis.
• Marked acanthosis, epidermal thickening.
• Auspitz sign of multiple punctate bleeding points when the scales are pulled off.

Histology:

• Elongation of the epidermal rete ridges, with thinning of the epidermis in the regions in between, forming a hair comb-like appearance.
• Increased epidermal cell turnover with lack of maturation, increased mitotic figures seen in the st. spinosum, and loss of the stratum granulosum.
• Extensive acanthosis due to thickening of the stratum corneum, with the distinctive sign of parakeratotic scale retention of nuclei in the s. corneum.
• Neutrophil invasion to the epidermis and especially the stratum corneum.
• Extensive dilated blood vessels in the papillae - cause the bleeding

Question 12

Presentation and symptoms of psoriasis

Answer 12

Most frequently occurs on the:

• scalp
• elbows
• knees
• breast folds
• intergluteal cleft (buttttt)
• glans penis

There are also fingernail and toenail changes in 1/3rd of cases.

Usually presents in specific regions, but uncommonly it can be disperesed and severe.

Only problems are the physical lesions, itching, but it can be very distressing. No proressive symptoms or risk.

Treatment:

NSAIDs, immunosuppression

Newer drugs target Th1 and Th17 cell responses.

Question 13

Morphology and histology of Lichen Planus

Answer 13

Lichen Planus

• Purple, Pruritic, Polygonal, Planar Papules and Plaques.
• (very faintly purple)
• Uncommon disorder seen in middle-aged adults.
• Multiple cutaneous lesions
• Symmetrically distributed on the extremities.
• Wrists, Elbows, Glans penis.
• 70% also involve oral mucosa, with white papules formed.
• The plaques often have meshed white lines running over them, called Wickham striae.
• The lesions last a long time, but spontaneously resolve over 1-2 years.
• Oral lesions may last longer and cause dysphagia.

Histology:

• Dense Lymphocytic infiltration at the dermis-epidermis junction
• Sawtoothig of the epidermis, with sharpening of the papillae into angular shapes.
• In contrast to psoriasis, where there is loss of the st. granulosum, and increasing nucleation of the st. corneum, in lichen planus, thetre is squamatization of the basal cells, in which they more rapidly lose their nuclei and take on st. spinosum appearance.
• Necrotic basal cells are also seen due to the inflammation, and are called Colloid bodies or Civatte bodies
• Hyperkeratosis and thickening of the epidermis, st. corneum.

Question 14

Lichen Simplex Chronicus, morphology, histology

Answer 14

Morphology:

• Roughening of the skin that becomes scaly and looks like tree bark/lichen. Caused by chronic repetitive trauma, scratching, friction.
• In its nodular form, its called Prurigo nodularis
• Pathogenesis is not clear, but basically: repetitive mechanical trauma -> epithelial hyperplasia and dermal scarring.
• Lesions are raised, erythematous and scaly.
• Can be mistaken for keratinocyte neoplasms.
• Often occur superimposed on top of other dermatoses secondarily.

Histology:

• Acanthosis: diffuse epithelial thickening, especially of the stratum basale and stratum spinosum.
• Rete ridge elognation
• Dermal fibrosis
• Chronic dermal inflammatory infiltration (not the specific lymphocytic infiltration around the dermal-epidermal border in the others)