Skin Pathology 1 Flashcards
What can skin lesion classification be based on?
- Underlying pathogenetic mechanism (used in this presentation)
- E.g. Vasculitis, immune-mediated disorder, inflammatory
- Lesion type (pruritus, alopecia, etc…)
- Distribution
- Aetiological agents (not always clarified)
What are the 2 broad layers?
- skin - cutis
- Subcutis
What are the different parts of the skin?
*Epidermis
*Dermis
*Hair follicle
*Sebaceous Gland
*Apocrine Gland
Histologically what is seen in the epidermis?
*Keratin
*Keratinocytes
*Desmosomes
*Melanocytes
What is the difference between primary and secondary hair follicle?
*Primary = Larger hairs, with
deeper bulb and with its own sebaceous and apocrine gland
*Secondary = Smaller one, with more superficial bulb and lack of apocrine gland
What is the difference between simple and compound follicle?
Simple = one hair per follicle
Compound = Multiple hair per follice
What are the 4 phases of hair follicles + the outcome/function?
*Anagen - growing HF
*Catagen - Regressing HF
*Telogen - Resting HF
*Kenogen - Latent (Hairless)
What are basic histological lesions of the skin?
*Acantholysis
*Epidermal hyperplasia
*Ballooning degeneration (intra-cellular oedema)
*Intercellular oedema (spongiosis)
*Dermatitis
*Flames figure
*Folliculitis & furuncolosis
*Hyperkeratosis (para & ortho)
*Vesicle
*(Micro)pustule
*Pigmentary incontinence
What occurs during hyperplasia?
*Increase in number of keratinocytes (usually increased epidermal thickness)
*Non-specific change, as usually secondary to a broad range of chronic different injuries (e.g. inflammation, parasites, friction)
What occurs during hyperkeratosis? What are the 2 different types?
*Orthokeratotic hyperkeratosis
*Parakeratotic hyperkeratosis
*Increase in thickness of the keratin layer with (parak.) or without (orthok.)
retention of the nucleus
*Can be primary (abnormal keratin production) or secondary (e.g inflammation)
What occurs during intercellular oedema (Spongiosis)?
*Oedema of the intercellular space between keratinocytes
* Usually associated to broad range of acute or subacute inflammatory dermatological diseases.
What occurs during intracellular oedema (Ballooning degeneration)?
*Oedema of keratinocytes showing swelling and cytoplasmic clearing
*Ballooning degeneration is used when the swelling is very severe.
*The latter is considered a characteristic change of viral infections
What is a vesicle?
*Intra-epidermal fluid-filled blister < 1cm in diameter
*It can be considered a severe expression of spongiosis and ballooning degeneration and caused by a broad range of acute and subacute injuries.
What is a (micro)pustule?
*Intra-epidermal accumulation of neutrophils
*Usually associated with bacterial or auto-immune conditions
What is Acantholysis?
*Detached and round keratinocytes showing cellular hypereosinophilia
*Hallmark of pemphigus complex disease, but can also be present in severe inflammatory neutrophilic or eosinophilic processes
What is dermatitis?
*Infiltration of inflammatory cells within the skin
*Can be elicited by numerous type of injuries
*Must be classified accordingly to the type of infiltrates (e.g. neutrophilic, eosinophilic, mixed)
What is folliculitis (Furunculosis)?
*Infiltration of inflammatory cells targeting hair follicles (inflammation of follicle)
*Can be located in any part of the hair follicle (e.g. lumen, wall)
*Can end up to destruction of the hair follicle with release of keratin in the dermis
(furunculosis)
What is a flame figure?
*Collagen bundles replaced by amorphous eosinophilic material
*Usually associated with conditions where there is strong eosinophilic infiltration (e.g. hypersensitivities, mast cell tumour).
What is pigmentary incontinence?
*Presence of melanocytes or melanin-laden macrophages within dermis
*Characteristic of any process ( e.g. inflammatory, neoplastic) basal cell damage, from where the melanocytes “fall” within the dermis.
What are the basic gross lesions?
*Crusts
*Ulcer
*Papula
*Nodule
*Bulla
*Pustule
*Comedo
*Lichenification
*Cyst
What is a nodule?
*Elevated, often firm, circumscribed, solid palpable lesion ≥1 cm in diameter.
*Can be neoplastic/inflammatory
What is a cyst?
*Cavity lined by epithelium and filled with liquid or semisolid material and located in the dermis or subcutis; may communicate with surface via a pore.
What is a vesicle/bulla
*Collections of fluid within or below the epidermis measuring < than 1 cm (vesicle) or >1.0 cm in diameter (bulla)
What is crust
*Dried exudate composed of various components, including fluid, blood, pustular debris, scale, or microorganisms on the skin surface
