Approach to Skin Morphology Flashcards
What are the 3 components of describing a skin lesion/defect?
1) Morphology
- primary, secondary, further characterisitics
2) Pattern
- single/multiple, arrangement, discrete/confluent
3) Distribution
- region/generalised, (a)symmetry, flexor/extensor, photodistributed sites
What is the similarity and difference between a macule and a patch?
Both circumscribed area of change in skin colour
Macule: <1cm
Patch: >1cm
What is the similarity and difference between a papule and a plaque?
Both circumscribed elevated area of skin
Papule: <1cm
Plaque: ≥1cm
What is the clinical definition of a nodule?
Circumscribed visible or palpable lump ≥1cm
What is the clinical definition of a wheal?
Rounded or flat-topped pale/red elevated area of cutaneous edema
- evanescent (transient)
- due to edema in papillary dermis → can change in size rapidly
What is the similarity and difference between a vesicle and a bulla?
Both circumscribed, elevated, superficial fluid-filled cavity
Vesicle: <1cm
Bullae: ≥1cm
What is the clinical definition of a pustule?
Circumscribed superficial cavity containing purulent exudate
- turbid
What is the clinical definition of a cyst?
A cavity containing liquid/semisolid lined by epithelium and a fibrous capsule
What is the similarity and difference between petechiae and purpura?
Both non-blanchable bleeding in the skin
Petechiae: smaller
Purpura: larger
What is the main concern if a px has specifically palpable purpura?
Vasculitis
What is the difference between a (i) erosion (ii) ulcer and (iii) fissure?
Erosion:
- defect only in epidermis
- typically complete resolution
Ulcer:
- defect extends to dermis or deeper
- heal with scarring
Fissure:
- narrow deep crack
What is the difference between (i) scale (ii) hyperkeratosis (iii) lichenification?
Scale:
- flaking of stratum corneum
Hyperkeratosis:
- thickening of stratum corneum w/o flaking off
Lichenification:
- thickening of skin 2° to chronic scratching, leathery exaggeration of normal skin lines
What is the clinical definition of a crust?
Dried serous/purulent/blood exudates
What is the clinical definition of skin atrophy?
Thinning of skin
- transparent
- telangiectasia
- loss of texture
- cigarette paper-like wrinkling
- depression
- bruising
What is the clinical definition of induration?
Dermal thickening causing cutaneous surface to feel thick, firm, tight
What is the clinical definition of a scar?
Fibrous tissue replacement of injury
What is a keloid?
Hypertrophy scar
What are 5 pointers for HPI rash?
1) When
2) Where
3) Itch, burn, pain?
4) Pattern of spread
5) Evolution
6) Provocative factors
7) Previous treatments a response
What are 5 characteristics in describing the morphology of skin rashes?
1) Shape
- discoid, annular, gyrate, serpiginous, oval, umbilicated, linear, unusual
2) Colour
- colour, variegated, woods lamp accentuation, blanching on diascope
3) Border
- well circumscribed/ill-defined
4) Palpation
- soft, fluctuant, hard, infiltrative, temperature, mobility, tenderness
5) Anatomic
- layers (epidermal, dermal, SQ, addpendageal)
What is a discoid shape in describing a skin lesion?
Coin shaped
eg. psoriasis → well defined
nummular eczema → less well defined
What is a common etiology of well-defined discoid shaped skin lesions?
Psoriasis
What is a targetoid shape in describing a skin lesion?
Circular lesion with 3 concentric zones of varying colours
What is the difference between typical and atypical target lesions?
Typical:
- ≥3 rings
- palpable
- eg. Erythema multiforme
Atypical:
- 2
- non-palpable
- eg. SJS/TEN
What is a typical cause of typical target lesions?
Erythema multiforme
What is a typical cause of atypical target lesions?
Steven Johnsons Syndrome/Toxic Epidermal Necrosis
What is Nikolsky’s sign?
Pull skin to side with shearing pressure →
if very thin top layer of skin shears off, leaving skin pink, moist and tender → blistering skin condition
What is a stellate shape in describing a skin lesion?
Star shaped
Septic vasculitis in meningococcemia usually produces what shaped skin lesions?
Stellate shaped
Polyarteritis nodosa and livedo vasculopathy usually produces what shaped skin lesions?
White stellate scars
What is a serpiginous shape in describing a skin lesion?
Snake like shape
Cutaneous larvae migrans usually causes what shaped skin lesions?
Serpiginous
Scabies usually causes what shaped skin lesions?
Serpiginous
What are 3 causes of linear patterned skin lesions?
1) Exogenous agents
2) Phytophotodermatitis
3) Hair dye allergy
4) Koebner phenomenon
5) Sporotrichosis
6) Thrombophlebitis
7) Inflammatory skin conditions
8) Autoinoculation
9) Infestations
What are 3 causes of yellow coloured skin lesions?
1) Cradle cap
- slightly greasy scaly plaque on scalp for babies
2) Xanthelasma
- on eyelids
3) Nevus sebaceous
- on scalp
What is a cause of purple skin lesions?
1) Lichen planus
- causes Wickham’s striae (classic feature of px with mucosal involvement of lichen planus)
2) Heliotrope rash
- over eyelids
What is the top clinical suspicion in a variegated skin lesion of various shades?
Melanoma
What is the clinical definition of exanthem?
Maculopapular eruption:
- Widespread skin eruption
- implies infectious or drug related etiology
What are 3 possible etiologies for skin lesions presenting on the intertriginous extensors?
1) Villitis herpetiformis
2) Psoriasis
3) Eczema
4) Cutaneous candidiasis
