Week 3: Rash

Question 1

Constructing a differential diagnosis for a rash in a young adult

Answer 1

What is a rash?
An inflammatory skin eruption
Differential diagnosis of a rash is primarily based on morphology of the lesion.
First identify the primary lesion, this is the lesion that is the typical element of the eruption.
Determine the global reaction pattern.
Distribution of the lesions. (diffuse, isolated, localized, regional, universal?)
Primary lesion: initial lesion that has not been altered by trauma or manipulation, and has not regressed
Secondary lesion: develops as the disease evolves or as the patient damages the lesion i.e. rubbing, scratching, infections.

Question 2

Bulla

Answer 2

A circumscribed, elevated lesion that
measures ≥ 1 cm and contains serous or hemorrhagic fluid (i.e., a large blister)

Question 3

Macule

Answer 3

A circumscribed, nonpalpable discolouration of the skin that measures <1 cm in diameter.

Question 4

Nodule

Answer 4

A palpable, solid, round ellipsoidal lesion measuring ≥ 1 cm; it differs from a plaque in that it is more substantive in its vertical dimension compared with its breadth.

Question 5

Papule

Answer 5

An elevated, solid lesion that measures < 1 cm.

Question 6

Patch

Answer 6

A circumscribed, nonpalpable discolouration of the skin that measures ≥ 1 cm.

Question 7

Petechiae

Answer 7

Nonblanching reddish macules representing extravascular deposits of blood, measuring ≤ 0.3 cm (less than the size of a pencil eraser).

Question 8

Circumscribed, elevated, fluid filled lesions

Answer 8

Bulla (> or = 1 cm) and Vesicle (< or = 1 cm)
pustule (may be follicular)

Question 9

Elevated and solid, differ in size

Answer 9

Nodule and papule

Question 10

Plaque

Answer 10

A palpable, solid lesion that measures ≥ 1 cm.

Question 11

Purpura

Answer 11

Nonblanching reddish macules or papules representing extravascular deposits of blood, measuring > 0.3 cm.

Question 12

Pustule

Answer 12

A lesion that contains pus; may be follicular (centered around a hair follicle) or nonfollicular.

Question 13

Vesicle

Answer 13

A circumscribed, elevated lesion that measures <1 cm and contains serous or hemorrhagic fluid (i.e., a small blister).

Question 14

Wheal

Answer 14

A round or annular (ring-like), edematous papule or plaque that is characteristically evanescent, disappearing within hours; may be surrounded by a flare or erythema (i.e., a hive)

Question 15

Photos

Answer 15

Question 16

Atrophy

Answer 16

A depression in the skin resulting from thinning of the epidermis, dermis and/or subcutaneous fat.

Question 17

Crust

Answer 17

A collection of dried blood, serum, and/or cellular debris.

Question 18

Erosion

Answer 18

A focal loss of epidermis does not penetrate below the dermal-epidermal junction and, therefore, can heal without scarring.

Question 19

Lichenification

Answer 19

Thickening of the epidermis resulting from repeated rubbing, appearing as accentuation of the skin markings.

Question 20

Scale

Answer 20

Excess dead epidermal cells; scale may be fine, silvery, greasy, desquamative, or adherent.

Question 21

Scar

Answer 21

Abnormal formation of connective tissue, implying dermal damage.

Question 22

Ulcee

Answer 22

A focal loss of full-thickness epidermis and partial to full-thickness dermis, which often heals with scarring

Question 23

Types of Global reaction pattern

Answer 23

Papulosquamous eruptions (Papules and plaques with scale)
Folliculopapular eruptions (perifollicular papules)
Dermal reaction patterns
Purpura and petechiae
Nonpalpable purpura
Blistering disorders (vesicles, pustules and bullae)

Question 24

History and Physical Exam

Answer 24

History in Dermatology
Include your standard HPI, past medical history, family medical history, social history, sexual history and the following key questions:
Key questions:
When? Onset
Where? Site of onset
Does it itch or hurt? Symptoms
How has it spread (pattern of spread)? Evolution
How have individual lesions changed? Evolution
Provocative factors? Heat, cold, sun, exercise, travel history, drugs, pregnancy, seasonal changes
Exposure(s) at the site? Changes to routines (laundry detergent, cosmetics, cleaning products etc.?
Previous treatment(s) and response to Treatment: Topical and systemic
Constitutional symptoms? Headaches, fever, chills, weakness, malaise arthralgias, etc.
More chronic ones – weight loss, weakness, malaise

Physical
General shape: round, oval, polygonal, polycyclic, annular (ring-shaped), iris, serpiginous (snakelike), umbilicated.
Size
Colour
Margination
Well defined
Ill defined
Palpation
Consistency (soft, firm, hard, fluctuant, board-like)
Deviation in temperature (hot, cold)
Mobility
Tenderness?
Estimate the depth of the lesion (i.e. dermal or subcutaneous)

Physical:
Number: Single or multiple lesions
Arrangement: Multiple lesions may be:
Grouped: herpetiform, arciform, annular, reticulated (net-shaped), linear, serpiginous
Disseminated: scattered discrete lesions
Confluence: Yes or no
Distribution:
Isolated?
Localized vs. regional vs. generalized
Pattern: symmetric, exposed areas, sites of pressure, intertriginous area, follicular localization, random, following dermatomes or Blashko lines

Question 25

Ruling out Melanoma and Dysplastic Nevi – The ABCDE’s

Answer 25

1. Asymmetry
2. Irregular Borders
3. Variegated Colour
4. Diameter – a lesion larger than 6 mm is at higher risk for malignancy
5. Evolution/Enlargement – a lesion that changes over time is at higher risk for malignancy

Question 26

Clinical and Laboratory Aids to Dermatological Diagnosis

Answer 26

Magnification with hand lens
Hand lens (7 x magnification)
Binocular microscope (5 x to 40x magnification)
Oblique lighting: Used to view degrees of elevation or depression in a lesion. Done in a darkened room.
Subdued lighting: Used to enhance the contrast between circumscribed hypopigmented or hyperpigmented lesions and normal skin.

Wood lamp (365 nm ultraviolet long-wave light, “black” light):
Can pick up fluorescent pigments and subtle colour differences of melanin pigmentation.
Causes some superficial lesions to fluoresce.
Vitiligo presents as amelanotic
Tinea capitis and tinea versicolor can sometimes be visualized with wood lamp but not likely tinea corporis, as many references would suggest – depends on the species of fungus
Porphyrias
Erythrasma
Some bacterial infections (pseudomonas)
Deep (reticular dermal) lesions typically do not fluoresce under a Wood lamp
Typically used by dermatologists, not necessary in naturopathic medical practice

Diascopy
Firmly pressing a microscopic slide or glass spatula over a skin lesion.
The examiner determined whether the red colour of a macule of papule is due to capillary dilatation (erythema) or due to extravasation of blood (purpura) that does not blanch.
Dermoscopy (also called epiluminescence microscopy)
A hand lens with built-in lighting and a magnification of 10x to 30x is called a dermatoscope and allows for inspection of deeper layers of the epidermis and beyond. Helpful to distinguish between a benign and malignant lesion.
These tools are typically used by dermatologists and not necessary in a naturopathic medical practice

Question 27

Clinical tests

Answer 27

Patch testing
Used to confirm a diagnosis of allergic contact sensitization and identify the agent that caused the allergic reaction.
Substances to be tested are applied to the skin in shallow cups (Finn chambers), taped onto the skin and left in place for 24 – 48 hours. Contact hypersensitivity will show as a papular vesicular reaction that will develop within 48 to 72 hours when the test is read.

Prick testing
Used to determine type I allergies
A drop of a solution containing a small amount of the allergen is placed on the skin and the skin is pierced through this drop with a needle.
A positive result would be a wheal appearing within 20 minutes.
Caution – the patient needs to be under constant supervision due to possibility of anaphylaxis.

Skin scraping
Dermatophyte/KOH Collection
Microscopic examination for mycelia should be made of the roofs of vesicles or of scales or in the hair in dermatophytosis.
The tissue is cleared with 10 to 30% KOH and warmed gently. Hyphae and spores can then be viewed.
Microbiology (Culture and Sensitivity) and Specimen Handling Biopsy
*Note most of these clinical tests are performed by allergists or dermatologist, some ND’s offer prick testing and skin scraping, but a patient can be referred out for further evaluation.

Biopsy
Different tools can be used for different types of lesions
Punch biopsy:
Useful in the work-up of cutaneous neoplasms, pigmented lesions, inflammatory lesions and chronic skin disorders.
3 to 4 mm punch, a small tubular knife cuts through the epidermis, dermis and subcutaneous tissue by rotating the tool.
Excisional biopsy (wide local excision)
Surgical removal of a tumour and some normal tissue around it.

Question 28

Differentials of a rash based on global reaction

Answer 28

(more charts on this in slides)

Question 29

Rash distribution

Answer 29

Question 30

Atopic Dermatitis

Answer 30

Question 31

Contact Dermatitis

Answer 31

Question 32

Seborrheic Dermatitis

Answer 32

Question 33

Dyshidrosis (acute palmplantar eczema)

Answer 33