Pruritis; Skin Rashes; Rash pathology

Question 1

Causal agent of scabies?

Answer 1

Cercoxi scabii

Inhabit the skin underneath the keratin layer

Arachnid

Nymph stage - 6 legs

Question 2

Where is itch processed?

Answer 2

Parts of forebrain and hypothalamus

Question 3

Mediators of itch

Answer 3

> Chemical mediators - histamine, PGE2, ACh, serotonin, kvllikrein, IL2, substance P tryptase.

> Nerve transmission - unmyelinated C fibres (different from pain)

> CNS - opiates, endogenous and exogenous

Question 4

Which type of antihistamines may help with itch?

Answer 4

sedating as they don’t cross the BBB.

Question 5

Degranulation of a mast cell

Answer 5

Release of pre formed mediators like tryptase, heparin and histamine

as well as

SYNTHESIS OF NEWLY FORMED MEDIATORS like prostaglandin D2, Leukotrienes C4, d4 and E4
and Platelet activating factor

Question 6

Causes of itch

Answer 6

PRURITOCEPTIVE: something in skin that triggers itch (dryness, inflammation)

NEUROPATHIC - damage of any sort to central or peripheral nerves causing itch

NEUROGENIC - no evident damage in CNS, but itch caused by e.g. opiate effects on CNS receptors

PSYCHOGENIC - psychological causes with no CNS damage

Question 7

Psychogenic cause of itch?

Answer 7

Delusions of infestation

Hypochondriacal condition.

Cocaine can cause it

Question 8

Endogenous opioids can be caused by?

Answer 8

Small bile duct obstruction - Primary Biliary Cirrhosis

Question 9

Dermographic skin

Answer 9

Stroking skin causes excessive mast cell degranulation and release of histamine and other mediators

Blood vessels become dilated and fluid moves to the surface

Question 10

What kind of nerves transmit itch?

Answer 10

Unmyelinated C fibres

Question 11

Xerotic eczema

Answer 11

Direct exposure of itch associated unmyelinated C fibres

causes itch

damaged epidermis/ keratin layer/ barrier function

dry skin

common in elderly and occurs in heated rooms.

Question 12

Breakfast Lunch and Supper sign

Answer 12

Insect bites/ bed bugs

bites which appear 3 in a row

Question 13

What kind of itching does lichen plants display?

Answer 13

Pruritoceptive.

Sometimes associated with chronic hep C infection

Itch caused by improper breakdown of compounds in liver.

Question 14

Prurigo nodularis

Answer 14

Skin disease characterised by pruritic (itchy) nodules

Question 15

Example of neuropathic itch?

Answer 15

Shingles

herpes zoster virus

Question 16

Can opiates cause itch?

If so, what type?

Answer 16

Yes. Neurogenic itch.

Question 17

Conditions that block bile ducts will cause…

Answer 17

Itch

Question 18

Hepatocellular disease has to be…

itch

Answer 18

Advanced in order for an itch to appear

Question 19

Does thyroid disease cause itch?

Answer 19

Yes

Question 20

Does Kidney disease cause itch?

Answer 20

Yes

Question 21

Carcinoma at head of pancreas obstructing the bile duct can cause…

Answer 21

itch

Question 22

In Primary Biliary Cirrhosis, does the itch come before or after bilirubin levels rise?

Answer 22

LONG before

? bile salts in skin

Question 23

Management of itch

Answer 23

> Determine cause (if possible)

> Treat the cause (easiest for pruritoreceptive itch)

> Anti-itch treatments

Question 24

Anti itch treatments

Answer 24

Sedative antihistamines

Emollients (menthol)

Antidepressants

Phototherapy

Opiate antagonists (ondansetron)

Neuropathic itch - anti epileptics.

Question 25

Assessment of any rash

Answer 25

Detailed hx Examination - distribution/sites affected - morphology - secondary features

Question 26

Commonest form of psoriasis

Answer 26

Chronic plaque psoriasis (psoriasis vulgaris) ``` Symmetrical Common sites -- extensors - scan, sacrum, hands, feet, trunk - nail ```

Question 27

Köbner phenomenon

Answer 27

Psoriasis develops in area of skin trauma e.g. scratch mark or scar

Question 28

Auspitz sign

Answer 28

Removal of surface scale reveals tiny bleeding points (dilated capillaries in elongated dermal papillae)

Question 29

Types of psoriasis

Answer 29

Guttate Palmoplantar pustular Erythrodermic Vulgaris

Question 30

Comorbidities of psoriasis

Answer 30

Psoriatic arthritis, metabolic syndrome (obesity, hypertension, diabetes, lipid abnormalities) Crohn's disease Cancer Depression Uveitis

Question 31

Pathogenesis of acne

Answer 31

Portal occlusion Build up of bacteria/ sebum behind portal occlusion Dermal inflammation Increased sebum production Poking spots makes it worse

Question 32

Distribution of acne vulgaris

Answer 32

Related to sites with most sebaceous glands Face, upper back, anterior chest

Question 33

Comedones

Answer 33

Open - blackhead | Closed - whitehead

Question 34

Features of acne vulgaris

Answer 34

Comedones Pustules and papules Cysts Erythema Scars atrophic, ice pick, texture changes, hypertrophic

Question 35

Acne Grading

Answer 35

Mild - scattered papule and pustules, comedones Moderate - numerous papule, pustules and mild atrophic scarring Severe - cysts, nodules and significant scarring

Question 36

What DON'T patients present with in rosacea

Answer 36

No comodones (black heads, white heads)

Question 37

Rosacea

Answer 37

Nose, chin , cheeks and forehead Papules, pustules, erythema NO COMEDONES Prominent facial flushing exacerbated by sudden change in temperature, alcohol and spicy food Enlarged unshapely nose - rhinopehyma Conjunctivitis

Question 38

Rhinophyma

Answer 38

Rounding of the nose Enlarged, unshapely nose

Question 39

Lichenoid eruptions

Answer 39

Damage and infiltration between the epidermis and dermis Lichen planus Lichenoid drug eruption

Question 40

Lichen planus

Answer 40

Violaceous (pin/purple) flat topped shiny papule Volar wrists, forearms, shins and ankles Wickham's striae - fine lace like pattern on surface of papule and buccal mucosa ITCHY

Question 41

Bullous pemphigoid

Answer 41

Split is DEEPER through DEJ Elderly patients Localised to one area or widespread on trunk/proximal limbs Large tense bull on normal skin on erythematous base Blisters burst --> erosions Non scarring Itchy eryhtematous plaques may be presenting feature Nikolsky sign NEGATIVE Mucosal involvement unlikely

Question 42

Bullous pemphigus

Answer 42

Split is more SUPERFICIAL, intra-epidermal Affects scalp, face, axillae, groins FLACID vesicles , bullae Lesions rupture to leave raw areas (increased infection) Nikolsky sign POSITIVE Mucosal involvement common HIGH MORTALITY IF UNTREATED

Question 43

Nikolsky's sign

Answer 43

Top layers of skin slip away from the lower layers when slightly rubbed Indicates plane of cleavage within the epidermis

Question 44

Where are melanocytes found?

Answer 44

Dermal-epidermal junction.

Question 45

Delayed pressure urticaria

Answer 45

Pressure urticaria is characterised by the appearance of weals after pressure to the skin