Ch0 Basic Principles Flashcards
What is erythema caused by
Erythema is caused by vasodilation and/or increased blood flow within the dermis
Entities that have the Koebner phenomenon
- psoriasis
- vitiligo
- lichen planus
- lichen nitidus
- cutaneous small vessel vasculitis
- Still disease
What does Woods lamp emit
UVA at 365 nm
How does a Woods lamp work
- lamp 4-5 inches away from where you are examining
- after the target absorbs the UVA radiation, there is some loss of energy and therefore the emission is at a longer wavelength within the visible range
What does vitiligo look like under woods lamp
chalk-white to dullish blue - fluorescence of dermal collagen observed due to a marked decrease or absence of melanin within the epidermis
Hyperpigmentation under Woods lamp
- Epidermal melanin –> enhances brown colour
- Dermal melanin –> difference between lesional and non-lesional skin becomes less obvious
Pseudomonas under Woods lamp
Green
Corynebacterium under Woods lamp
Coral red
P acnes under woods lamp
Orange-red (in comedones)
Pit versicolor under Woods lamp
Yellowish-white
Yellow-green
Golden
Copper-orange
Tinea capitis under Woods lamp due to Microsporun
Blue-green to yellow-green
Trichophyton schoenleinlii under Woods lamp
blue-wehite
How long does parakeratosis take to develop (scale)
2 weeks
How long does tense bullae last for
less than a week
Causes of a rash and fever
- Infectious
- Bacteria: toxic shock, SSSS, scarlet fever, septic emboli, secondary syphilis
- Viruses: exanthems, disseminated zoster
- Fungi
- Protozoa
- Kawasaki
- Inflam:
- Drug reactions - DRESS< AGEP
- EM, SJS
- Primary cutaneous disorders
- Rheum disorders
- GVHD
- Neoplastic: lymphoma
- Inherited
Acute cutaneous eruptions in otherwise healthy individuals
- urticaria
- acute allergic contact dermatitis, ICD
- Drug eruptions
- Pit rosea
- Viral exanthems
Where to biopsy in vasculitides
Centre of early lesion
Where to biopsy in livedo reticularis
centre of pale areas defined by surrounding venous plexus network, corresponds to site of ascending arteriole
Where to biopsy CT disease
fully developed lesion, not scarred
Where to biopsy alopecia
Active advancing edge, ares of perifollicular inflammation
Where to biopsy infectious
Mature lesions, if ulcerated inflammatory border
Ulcerative dermatoses where to biopsy
Active edge of ulcer or early lesion
Where to biopsy pigmentary lesion
Get non-lesional skin as well
Where to biopsy urticaria
Edge of lesion as well
Vacuolar definition
Degeneration of basilar keratinocytes with little or no inflammation
Lichenoid definition
lymphocytes directly engaged in the destruction of basilar keratinocytes
Spongiosis definition
- intercellular oedema, widened spaces between keratinocytes with elongation of intercellular bridges. Often associated with exocytosis of inflammatory cells
- Acute, subacute, chronic
- When chronic - may be more acanthosis (thickening of the epidermis)
Psoriasiform definition
Epidermal hyperplasia - elongation of rete ridges
Pseudoepitheliomatous hyperplasia definition
related to psoriasiform - irregular, hyperplasia of the epidermis and/or adnexal structures. Can occur from chronic rubbing/scratching, but can be with inflammatory etc
Acantholysis definition
- discohesion of keratinocytes due to disruption of desmosomes
- Identifying level of epidermis
Ballooning degeneration definition
intracellular oedema in response to cytotoxic events –> presence of abundant pale cytoplasm of keratinocytes in the spinous zone. When ballooning is severe –> keratinocyte rupture –> reticular degeneration and epidermal necrosis
Granulomatous vasculitis
histiocytes within and around BV walls with fibrin/degenerative and necrotic changes. Seen in a restricted group of diseases: GPA, EGPA, temporal arteritis
Nodular and diffuse dermatitis definition
similar to perivascular dermatitis, but inflammatory infiltrate has enlarged and coalesced to form one or multiple nodules within the dermis
4 histopathologic types of granulomas
- Tuberculoid –> epithelioid histiocytes, surrounded by a dense infiltrate of lymphocytes and plasma cells, +/- central caseation. May be Langhan type, associated with cutaneous infections, lupus miliaris
- Sarcoidal –> epithelioid histiocytes with minimal lymphocytic infiltrate - naked tubercles
- Palisaded ‘necrobiotic’ - epithelioid histiocytes aligned as a rim around a central area of degenerated collagen with different tinctorial qualities. All palisaded granulomas are markedly palisaded, and histiocytes may be distributed interstitially –> interstitial granuloma
- Suppurative –> comprised of neutrophils within and sometimes among or surrounding, aggregates of epithelioid histiocytes
Langerhan cell histiocytosis brief histo overview
reniform (kidney bean-shaped) nuceli, positive for S100, CD207 and CD1a
Non-LCH brief histo overview
range of cytologic features - vacuolated, spindle shaped, foamy, scalloped, oncocytic. S100-, CD1a- and CD68+ (nonspecific marker of histiocyte lineage)
Lipophage definition
Foamy histiocytes filled with lipid
Questions to ask when assessing panniculitis
- septal or lobular?
- vasculitis or no?
- type of inflammatory infiltrate?
- cytologic atypia?
- fat necrosis - hyaline changes, basophilic saponification
Causes of invisible dermatoses
Stratum corneum:
Superficial infections - tinea versicolor, dermatophytosis, erythrasma, pitted keratolysis
Keratinization: ichthyosis, DSAP
Basilar layer - pigment issues: vitiligo, melasma, CALM
Superficial dermis:
Infestations - onchocerciasis,
Mast cells: TMEP
Endogenous deposition: macular amyloidosis
Superficial and deep:
Exogenous substance: argyria
Endogenous: systemic amyloidosis
Collagen: collagenoma, atrophoderma
Elastic tissue: naevus elasticus, anetoderma
Absence of normal epithelial structure:
hypohidrotic ectodermal dysplasia