Approach to Skin Morphology

Question 1

What are the 3 components of describing a skin lesion/defect?

Answer 1

1) Morphology
- primary, secondary, further characterisitics

2) Pattern
- single/multiple, arrangement, discrete/confluent

3) Distribution
- region/generalised, (a)symmetry, flexor/extensor, photodistributed sites

Question 2

What is the similarity and difference between a macule and a patch?

Answer 2

Both circumscribed area of change in skin colour

Macule: <1cm
Patch: >1cm

Question 3

What is the similarity and difference between a papule and a plaque?

Answer 3

Both circumscribed elevated area of skin

Papule: <1cm
Plaque: ≥1cm

Question 4

What is the clinical definition of a nodule?

Answer 4

Circumscribed visible or palpable lump ≥1cm

Question 5

What is the clinical definition of a wheal?

Answer 5

Rounded or flat-topped pale/red elevated area of cutaneous edema
- evanescent (transient)
- due to edema in papillary dermis → can change in size rapidly

Question 6

What is the similarity and difference between a vesicle and a bulla?

Answer 6

Both circumscribed, elevated, superficial fluid-filled cavity

Vesicle: <1cm
Bullae: ≥1cm

Question 7

What is the clinical definition of a pustule?

Answer 7

Circumscribed superficial cavity containing purulent exudate

• turbid

Question 8

What is the clinical definition of a cyst?

Answer 8

A cavity containing liquid/semisolid lined by epithelium and a fibrous capsule

Question 9

What is the similarity and difference between petechiae and purpura?

Answer 9

Both non-blanchable bleeding in the skin

Petechiae: smaller
Purpura: larger

Question 10

What is the main concern if a px has specifically palpable purpura?

Answer 10

Vasculitis

Question 11

What is the difference between a (i) erosion (ii) ulcer and (iii) fissure?

Answer 11

Erosion:
- defect only in epidermis
- typically complete resolution

Ulcer:
- defect extends to dermis or deeper
- heal with scarring

Fissure:
- narrow deep crack

Question 12

What is the difference between (i) scale (ii) hyperkeratosis (iii) lichenification?

Answer 12

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

Question 13

What is the clinical definition of a crust?

Answer 13

Dried serous/purulent/blood exudates

Question 14

What is the clinical definition of skin atrophy?

Answer 14

Thinning of skin
- transparent
- telangiectasia
- loss of texture
- cigarette paper-like wrinkling
- depression
- bruising

Question 15

What is the clinical definition of induration?

Answer 15

Dermal thickening causing cutaneous surface to feel thick, firm, tight

Question 16

What is the clinical definition of a scar?

Answer 16

Fibrous tissue replacement of injury

Question 17

What is a keloid?

Answer 17

Hypertrophy scar

Question 18

What are 5 pointers for HPI rash?

Answer 18

1) When
2) Where
3) Itch, burn, pain?
4) Pattern of spread
5) Evolution
6) Provocative factors
7) Previous treatments a response

Question 19

What are 5 characteristics in describing the morphology of skin rashes?

Answer 19

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)

Question 20

What is a discoid shape in describing a skin lesion?

Answer 20

Coin shaped
eg. psoriasis → well defined
nummular eczema → less well defined

Question 21

What is a common etiology of well-defined discoid shaped skin lesions?

Answer 21

Psoriasis

Question 22

What is a targetoid shape in describing a skin lesion?

Answer 22

Circular lesion with 3 concentric zones of varying colours

Question 23

What is the difference between typical and atypical target lesions?

Answer 23

Typical:
- ≥3 rings
- palpable
- eg. Erythema multiforme

Atypical:
- 2
- non-palpable
- eg. SJS/TEN

Question 24

What is a typical cause of typical target lesions?

Answer 24

Erythema multiforme

Question 25

What is a typical cause of atypical target lesions?

Answer 25

Steven Johnsons Syndrome/Toxic Epidermal Necrosis

Question 26

What is Nikolsky’s sign?

Answer 26

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

Question 27

What is a stellate shape in describing a skin lesion?

Answer 27

Star shaped

Question 28

Septic vasculitis in meningococcemia usually produces what shaped skin lesions?

Answer 28

Stellate shaped

Question 29

Polyarteritis nodosa and livedo vasculopathy usually produces what shaped skin lesions?

Answer 29

White stellate scars

Question 30

What is a serpiginous shape in describing a skin lesion?

Answer 30

Snake like shape

Question 31

Cutaneous larvae migrans usually causes what shaped skin lesions?

Answer 31

Serpiginous

Question 32

Scabies usually causes what shaped skin lesions?

Answer 32

Serpiginous

Question 33

What are 3 causes of linear patterned skin lesions?

Answer 33

1) Exogenous agents
2) Phytophotodermatitis
3) Hair dye allergy
4) Koebner phenomenon
5) Sporotrichosis
6) Thrombophlebitis
7) Inflammatory skin conditions
8) Autoinoculation
9) Infestations

Question 34

What are 3 causes of yellow coloured skin lesions?

Answer 34

1) Cradle cap
- slightly greasy scaly plaque on scalp for babies

2) Xanthelasma
- on eyelids

3) Nevus sebaceous
- on scalp

Question 35

What is a cause of purple skin lesions?

Answer 35

1) Lichen planus
- causes Wickham’s striae (classic feature of px with mucosal involvement of lichen planus)

2) Heliotrope rash
- over eyelids

Question 36

What is the top clinical suspicion in a variegated skin lesion of various shades?

Answer 36

Melanoma

Question 37

What is the clinical definition of exanthem?

Answer 37

Maculopapular eruption:
- Widespread skin eruption
- implies infectious or drug related etiology

Question 38

What are 3 possible etiologies for skin lesions presenting on the intertriginous extensors?

Answer 38

1) Villitis herpetiformis
2) Psoriasis
3) Eczema
4) Cutaneous candidiasis