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Dermatology > Pruritis; Skin Rashes; Rash pathology > Flashcards

Pruritis; Skin Rashes; Rash pathology Flashcards

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Dermatology Board Prep flashcards
1
Q

Causal agent of scabies?

A

Cercoxi scabii

Inhabit the skin underneath the keratin layer

Arachnid

Nymph stage - 6 legs

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2
Q

Where is itch processed?

A

Parts of forebrain and hypothalamus

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3
Q

Mediators of itch

A

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

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

> CNS - opiates, endogenous and exogenous

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4
Q

Which type of antihistamines may help with itch?

A

sedating as they don’t cross the BBB.

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5
Q

Degranulation of a mast cell

A

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

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6
Q

Causes of itch

A

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

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7
Q

Psychogenic cause of itch?

A

Delusions of infestation

Hypochondriacal condition.

Cocaine can cause it

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8
Q

Endogenous opioids can be caused by?

A

Small bile duct obstruction - Primary Biliary Cirrhosis

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9
Q

Dermographic skin

A

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

Blood vessels become dilated and fluid moves to the surface

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10
Q

What kind of nerves transmit itch?

A

Unmyelinated C fibres

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11
Q

Xerotic eczema

A

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.

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12
Q

Breakfast Lunch and Supper sign

A

Insect bites/ bed bugs

bites which appear 3 in a row

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13
Q

What kind of itching does lichen plants display?

A

Pruritoceptive.

Sometimes associated with chronic hep C infection

Itch caused by improper breakdown of compounds in liver.

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14
Q

Prurigo nodularis

A

Skin disease characterised by pruritic (itchy) nodules

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15
Q

Example of neuropathic itch?

A

Shingles

herpes zoster virus

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16
Q

Can opiates cause itch?

If so, what type?

A

Yes. Neurogenic itch.

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17
Q

Conditions that block bile ducts will cause…

A

Itch

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18
Q

Hepatocellular disease has to be…

itch

A

Advanced in order for an itch to appear

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19
Q

Does thyroid disease cause itch?

A

Yes

20
Q

Does Kidney disease cause itch?

A

Yes

21
Q

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

A

itch

22
Q

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

A

LONG before

? bile salts in skin

23
Q

Management of itch

A

> Determine cause (if possible)

> Treat the cause (easiest for pruritoreceptive itch)

> Anti-itch treatments

24
Q

Anti itch treatments

A

Sedative antihistamines

Emollients (menthol)

Antidepressants

Phototherapy

Opiate antagonists (ondansetron)

Neuropathic itch - anti epileptics.

25
Q

Assessment of any rash

A

Detailed hx

Examination

  • distribution/sites affected
  • morphology
  • secondary features
26
Q

Commonest form of psoriasis

A

Chronic plaque psoriasis (psoriasis vulgaris)

Symmetrical 
Common sites
-- extensors
- scan, sacrum, hands, feet, trunk
- nail
27
Q

Köbner phenomenon

A

Psoriasis develops in area of skin trauma

e.g. scratch mark or scar

28
Q

Auspitz sign

A

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

29
Q

Types of psoriasis

A

Guttate
Palmoplantar pustular
Erythrodermic
Vulgaris

30
Q

Comorbidities of psoriasis

A

Psoriatic arthritis, metabolic syndrome (obesity, hypertension, diabetes, lipid abnormalities)

Crohn’s disease

Cancer

Depression

Uveitis

31
Q

Pathogenesis of acne

A

Portal occlusion

Build up of bacteria/ sebum behind portal occlusion

Dermal inflammation

Increased sebum production

Poking spots makes it worse

32
Q

Distribution of acne vulgaris

A

Related to sites with most sebaceous glands

Face, upper back, anterior chest

33
Q

Comedones

A

Open - blackhead

Closed - whitehead

34
Q

Features of acne vulgaris

A

Comedones
Pustules and papules
Cysts
Erythema

Scars atrophic, ice pick, texture changes, hypertrophic

35
Q

Acne Grading

A

Mild - scattered papule and pustules, comedones

Moderate - numerous papule, pustules and mild atrophic scarring

Severe - cysts, nodules and significant scarring

36
Q

What DON’T patients present with in rosacea

A

No comodones (black heads, white heads)

37
Q

Rosacea

A

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

38
Q

Rhinophyma

A

Rounding of the nose

Enlarged, unshapely nose

39
Q

Lichenoid eruptions

A

Damage and infiltration between the epidermis and dermis

Lichen planus
Lichenoid drug eruption

40
Q

Lichen planus

A

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

41
Q

Bullous pemphigoid

A

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

42
Q

Bullous pemphigus

A

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

43
Q

Nikolsky’s sign

A

Top layers of skin slip away from the lower layers when slightly rubbed

Indicates plane of cleavage within the epidermis

44
Q

Where are melanocytes found?

A

Dermal-epidermal junction.

45
Q

Delayed pressure urticaria

A

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

Dermatology (8 decks)

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