Skin Pathology Flashcards
Describe the normal structure of the skin, from superficial to deep
Epidermis:
- Thin, avascular layer
- Keratenocytes
- Renewed every 1530 days
Dermis:
- Highly vascular layer of the skin
- The main support structure
- Elastic and collagen
Subcutaneous tissue
- Fatty tissue
- Shock absorber
What are the main categories of skin disorders? Give examples of each
Vesiculobullous
- Dermatitis herpetiformis
- Pemphigoid
- Pemphigus
Spongiotic
- Dermatitis
Psoriasiform
- Psoriasis
Lichenoid
- Lichen planus
Vasculitis
- Pyoderma gangrenosum
Granulomatous
Describe dermatitis
A group of disorders with the same histology, presenting with a dry itchy rash
Histology:
- Acute: spongiosis, inflammatory infiltrate, dilated capillaries
- Chronic: acanthosis, crusting, scaling
Atopic dermatitis
- Flexural areas
- Infants: face and scalp
- Lichenification in chronic cases
- FHx of atopy
Contact dermatitis
- Type IV hypersensitivity (e.g. nickel, rubber)
- Commonly ear lobes and neck, wrist and feet
Suborrhoeic dermatitis
- Reaction to yeast
- Infants: cradle cap
- Young adults: mild erythema, fine scaling
Describe psoriasis
A common inflammatory condition caused by an increased proliferation rate of the skin.
Histology:
- Parakeratosis
- Loss of granular layer
Chronic plaque psoriasis
- Salmon pink plaques with silver scale
- Pinpoint bleeding when rubbed
Other forms:
- Flexural: seen inelderly, groin
- Guttate: rain-drop plaques, post strep
- Erythrodermic/pustular: severe and widespread
Associations: nails
- Pitting
- Onycholisis
- Subungual hyperkeratosis
Describe lichen planus
5 Ps:
- Pruritis
- Purple
- Polygonal
- Papules
- Plaques
Usually on wrists, but can affect mucosal layers
Histology:
- hyperkeratosis
- Saw-toothing of rete ridges
Describe erythema multiforme
Causes annular target lesions, on hands and feet
Causes:
- HSV, mycoplasma
- SNAPP (sulphonamides, NSAIDs, allopurinol, penicillin, phenytoin)
Describe Stevens Johnson Syndrome and Toxic Epidermal Necrolysis
Dermatological emergency with sheets of skin detachment
- SJS: <10 of skin surface
- TEN: >30 of skin surface
Commonly caused by drugs sulphonamides, anticonvulsants)
Describe pityriasis rosea
Salmon pink herald patch, then spreads in Christmas tree distribution
Commonly post viral infection and resolves spontaneously
Describe the dermatitis herpetiformis, bullous pemphigoid and pemphigus vulgaris
Dermatitis herpetiformis
- Patho: coeliac disease, IgA binds to basement membrane
- Itchy vesicles on extensor surface of elbows
- Histo: microabscesses, forming subepidermal bullae and IgA deposits
Bullous pemphigoid
- Patho: IgG deposition at hemidesmosomes
- Tense bullar on erythematous base on forearm and groin; bullae do not rupture easily
Histo: supepidermal bullae with linear IgG deposits
Pemphigus vulgaris
- Patho: IgA deposition on desmosomal proteins
- Bullae easily ruptured, found on skin and mucosa
- Histo: intraepidermal bullae with netlike IgG deposits
Describe some benign and pre-malignant cutaneous neoplasms
Benign:
- Seborrheoic keratosis, rough waxy plaques
Pre-malignant
Actinic keratosis:
- Rough, sandpaper like scaly lesions
- SPAIN (solar elastosis, parakeratosis, atypia, inflammation, not full thickness)
Keratoacanthoma:
- Rapidly growing dome shaped nodule, central crusted area
- Grows over 2-3 weeks then clears
- Similar to SCC histology
Bowen’s disease:
- Intra-epidermal SCC in situ
- Flat, red, scaly patches
- Full thickness dysplasia on histology, basement membrane intact
Describe some malignant cutaneous neoplasms
Basal cell carcinoma
- Rodent ulcer
- Pearly edges, central ulceration, telangiectasia
- Mass of cells pushing down into dermal layer
- Local invasion, but rare metastasis
Squamous cell carcinoma
- Bowen’s disease + basement membrane invasion
- Atypia in epidermis, spreading through basement membrane
Describe malignant melanoma
Benign version: moles, junctional, compound or intradermal
Malignant
- ABCDE (asymmetry, border, colour, diameter, evolution)
- Histo: atypical melanocytes, grow horizontally, then down
- Prognosis: Breslow’s thickness (>4mm is very bad)
Subtypes:
- Lentigo maligna melanoma: elderly, flat, slow growing
- Superficial spreading malignant melanoma: irregular borders with variation in colour
- Nodular malignant melanoma: more common in younger age groups
- Acral lentiginous melanoma: palms, soles and subungual areas
