Dermatology > Module 4: Pruritus > Flashcards

Module 4: Pruritus Flashcards

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1
Q

What is pruritus?

A

Pruritus is an unpleasant sensation that elicits the desire to scratch.

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2
Q

Where does the sensation of pruritus originate?

A

Afferent sensory nerve fibres in the skin detect the itch stimulus.

The signal is processed through the spinal cord and brain, particularly the reward centre, reinforcing the itch-scratch cycle.

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3
Q

What is the “itch-scratch cycle”?

A

Scratching temporarily relieves itch but activates the same nerve pathways, leading to further itching and scratching, perpetuating the cycle.

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4
Q

What are the main sources of pruritus?

A

Chemical mediators (e.g. histamine)

CNS or PNS disorders

Systemic diseases

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5
Q

Which chemical mediator is most commonly involved in pruritus?

A

Histamine, released from mast cells in allergic or inflammatory reactions.

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6
Q

Name other mediators that can cause pruritus.

A

Serotonin, prostaglandins, cytokines, bile salts, and opioids.

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7
Q

How can CNS or PNS disorders cause pruritus?

A

Damage or dysfunction of nerve pathways (e.g., post-herpetic neuralgia, multiple sclerosis, brain tumours) can generate neuropathic itch

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8
Q

Name some systemic diseases that can present with pruritus.

A

Cholestasis (bile salt accumulation)

Chronic renal failure (uraemia)

Thyroid disorders (esp. hyperthyroidism)

Hodgkin lymphoma

Polycythaemia vera (after warm bath)

Diabetes mellitus

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9
Q

What is scabies?

A

Scabies is a contagious parasitic infestation caused by the mite Sarcoptes scabiei.

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10
Q

What is a key clue in the history suggesting scabies?

A

Other family members or close contacts are also itchy.

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11
Q

What are the characteristic features of scabies rash?

A

Intense itching, especially at night

Burrows, papules, or vesicles

Commonly affects finger webs, wrists, axillae, waistline, genitals

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12
Q

What is contact eczema?

A

Inflammatory skin reaction caused by exposure to an irritant or allergen.

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13
Q

What important history points suggest contact eczema

A

Recent exposure to new substances (e.g. soaps, detergents, metals, cosmetics)

Occupational exposure

Localized rash where skin contacts the irritant

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14
Q

What are the two main types of contact eczema?

A

Irritant contact dermatitis

Allergic contact dermatitis

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15
Q

What is urticaria?

A

Urticaria is a transient, itchy, raised, erythematous rash (wheals) due to histamine release from mast cells.

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16
Q

What is characteristic of urticarial lesions?

A

Lesions come and go within minutes to hours

No scaling or crusting

May be triggered by food, drugs, or infection

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17
Q

What key history point suggests urticaria?

A

Itching that comes and goes, often associated with a new medication or food exposure.

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18
Q

What does pruritus with normal skin indicate?

A

It suggests systemic or internal causes rather than primary skin disease.

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19
Q

What systemic conditions can cause pruritus without skin lesions?

A

Liver disease – e.g., cholestasis or biliary obstruction

Kidney disease – e.g., chronic renal failure (uraemic pruritus)

Thyroid disease – especially hyperthyroidism

Iron deficiency

Lymphoproliferative disorders – e.g., lymphoma, leukemia

Psychological causes – stress, anxiety, or somatoform disorders

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20
Q

What is the initial approach to a patient with pruritus and normal skin?

A

General health history – systemic symptoms, medications, family history

Physical examination – check for:
-Pallor (anaemia)
-Jaundice (liver disease)
-Lymphadenopathy (lymphoproliferative disease)

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21
Q

What laboratory tests are indicated?

A

Liver function: Conjugated bilirubin (cholestasis)

Renal function: Creatinine, urea (kidney disease)

Thyroid function: TSH

Haematology: Iron, haemoglobin

Inflammatory markers: ESR or CRP (rule out systemic inflammatory or malignant disease)

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22
Q

What type of eczema is a common cause of pruritus in children?

A

Atopic eczema (atopic dermatitis), especially in young children.

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23
Q

What are the typical features of atopic eczema?

A

Itchy, dry, red, and inflamed skin

Flexural involvement (elbows, knees)

Chronic scratching → lichenification

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24
Q

How does scabies present?

A

Intense itching, often worse at night

Burrows and papules, especially on finger webs, wrists, and genitals

May involve all ages

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25
What is papular urticaria?
A hypersensitivity reaction to insect bites, common in children.
26
How does it present of papular urticaria
Grouped itchy papules, often on exposed skin
27
What is PPE? PAPULAR PRURITIC ERUPTION
Papular pruritic eruption seen in HIV-infected patients, often symmetrical on limbs and trunk.
28
Key feature of PAPULAR PRURITIC ERUPTION OF HIV (PPE)
Severe pruritus with papular rash, may indicate advanced HIV
29
How does urticaria (hives) present?
Transient raised erythematous wheals Intense itching Lesions come and go within hours Triggered by food, medications, or infections
30
How do fungal infections cause pruritus?
Dermatophyte infections (tinea) cause itchy, scaly, ring-shaped lesions, often localized.
31
Examples of fungal infection
Tinea corporis, tinea pedis, tinea capitis
32
Who is most affected by dry skin–related pruritus?
Elderly patients
33
Features of DRY SKIN (XEROSIS)
Dry, rough, flaky skin Mild redness and generalized itch, especially in winter
34
What is atopic dermatitis (eczema)?
A chronic, relapsing inflammatory skin disorder characterized by itching, dry skin, and eczematous lesions, commonly seen in young children.
35
Why is atopic dermatitis clinically important?
It is a very common cause of itching and often leads to poor sleep in children due to intense pruritus.
36
What is the typical distribution of atopic dermatitis?
Infants: Face, scalp, extensor surfaces Children: Flexural areas (elbows, knees, wrists, ankles) Adults: Hands, eyelids, and flexural regions
37
What systemic or familial clues support a diagnosis of atopic dermatitis?
Family history of atopy — asthma, allergic rhinitis, or eczema
38
What are key skin findings of atopic dermatits
Dry, red, itchy plaques Lichenification from chronic scratching Excoriations and possible secondary infection
39
What are the main components of atopic dermatitis management?
Moisturizers (emollients): Applied regularly to maintain skin barrier Topical corticosteroids: To reduce inflammation during flares Avoidance of irritants/triggers: Soaps, detergents, harsh fabrics, allergens Additional measures: Antihistamines for sleep, topical calcineurin inhibitors in selected cases
40
What features help diagnose atopic dermatitis?
Chronic or relapsing itchy rash Typical distribution according to age Dry skin (xerosis) Personal or family history of atopy (asthma, allergic rhinitis, eczema) Early onset, usually in infancy or early childhood
41
What is papular urticaria?
A hypersensitivity reaction to insect bites, most commonly seen in children.
42
What is the characteristic pattern of lesions in papular urticaria?
Lesions often appear in linear arrangements, sometimes called “breakfast, lunch, and supper” pattern.
43
What is notable about the stage of the lesions in papular urticaria
Lesions are in different stages — some new, some healing, some crusted.
44
Is there any area typically spared in babies in papular urticaria
Yes, the nappy (diaper) area is usually spared
45
How do lesions heal in papular urticaria
With hyperpigmentation
46
What is the main treatment for papular urticaria?
Topical corticosteroids to reduce inflammation and itching.
47
What additional management strategies can help with papular urticaria
Avoid insect exposure (nets, repellents) Antihistamines for severe itch Keep nails short to prevent secondary infection from scratching
48
What is papular pruritic eruption (PPE)?
PPE is a form of papular urticaria seen in immunosuppressed individuals, especially HIV-infected patients.
49
What is the typical distribution of PPE?
Usually limbs > trunk; less commonly on the face.
50
What are key diagnostic clues of PPE?
Linearity of lesions Lesions in different stages (new, healing, crusted) Severe pruritus
51
How is PPE related to papular urticaria?
PPE is considered a variant of papular urticaria, triggered by hypersensitivity reactions in immunosuppressed patients.
52
What is the main treatment for PPE?
Topical corticosteroids to reduce inflammation and itch.
53
What important condition should be ruled out before treatment?
Scabies, as it can mimic PPE.
54
What is urticaria?
Urticaria, also known as “hives”, is a transient, itchy, raised rash caused by histamine release from mast cells.
55
What are the characteristic features of urticaria lesions?
Raised wheals (papules or plaques) Come and go, typically lasting <24 hours Resolve without leaving a mark
56
What are common triggers of urticaria
Medications (including over-the-counter drugs) Foods Drinks Sometimes infections or physical stimuli
57
hat is the main treatment for urticaria?
Oral antihistamines to reduce itching and inflammation.
58
What additional management strategies may be used for urticaria
Avoid known triggers Severe cases may require short course corticosteroids Epinephrine for anaphylaxis if associated with angioedema
59
What is scabies?
Scabies is a contagious skin infestation caused by the mite Sarcoptes scabiei, leading to intense itching.
60
Which areas are typically involved in scabies?
Wrists Finger webs Periumbilical area Buttocks Can also involve ankles, genitalia, and elbows
61
What is a characteristic skin lesion of scabies?
Burrows — linear or S-shaped tracks in the skin
62
What family or social clue supports the diagnosis?
Other family members or close contacts are also itchy, often at night.
63
What is the main treatment for scabies?
Topical benzyl benzoate (applied over the whole body, usually repeated after 1 week).
64
What additional management is important?
Treat all close contacts simultaneously Wash bedding and clothes in hot water Trim nails to reduce secondary infection
65
What is tinea?
Tinea is a superficial fungal infection of the skin caused by dermatophytes (e.g., Trichophyton, Microsporum, Epidermophyton).
66
What is the characteristic appearance of tinea lesions?
Ring-shaped (annular) plaques with: Active raised edge Central clearing
67
Why does the center of the lesion clear?
The fungal infection is active at the periphery, while the center heals as the infection spreads outward.
68
Where can tinea infections occur?
Anywhere on the body: Tinea corporis: body Tinea pedis: feet Tinea capitis: scalp Tinea cruris: groin
69
What is the main treatment for tinea?
Topical antifungal creams (e.g., clotrimazole, miconazole) for localized infections.
70
What if the infection is widespread or scalp involvement?
Oral antifungals (e.g., terbinafine, griseofulvin) may be required.
71
What is pruritus due to dry skin?
It is itching caused by xerosis, often associated with rough, flaky skin without primary skin lesions.
72
Who is most commonly affected by dry skin–related pruritus?
Elderly patients.
73
What factors can worsen pruritus in dry skin?
Frequent use of soaps or harsh detergents Low humidity environments Hot baths or showers
74
How does the skin typically appear?
Dry, rough, flaky skin Mild redness may be present Usually generalized itch
75
What is the main treatment for pruritus due to dry skin?
Regular use of emollients / moisturizers to restore the skin barrier Avoid harsh soaps and prolonged hot showers Mild topical corticosteroids if inflammation occurs
76
What are excoriations?
Excoriations are secondary skin lesions caused by scratching.
77
What do excoriations look like?
Dug-out areas of skin Small, nail-sized erosions or linear scratches May crust or bleed if scratched repeatedly
78
How can the location of excoriations be clinically useful?
They often appear in easy-to-reach areas, giving a clue about self-inflicted scratching.
79
In which patients are excoriations commonly seen?
Any patient with pruritus from systemic disorders (e.g., liver, kidney, or thyroid disease) Psychological disorders (e.g., anxiety, OCD, psychogenic pruritus)
80
How are excoriations managed?
Treat the underlying cause of itch (dermatologic, systemic, or psychological) Topical emollients to protect the skin Topical corticosteroids if inflammation is present Behavioral strategies to reduce scratching
81
What is nodular prurigo?
Nodular prurigo is a chronic skin condition characterized by itchy, hyperkeratotic nodules caused by persistent scratching.
82
What do nodular prurigo lesions look like?
Hyperkeratotic nodules Pigmented (often brownish) Rough surface Usually very itchy
83
What causes nodular prurigo?
Chronic scratching or rubbing of the skin, often secondary to long-standing pruritus.
84
Where do lesions typically occur?
Commonly on extensor surfaces, limbs, and areas accessible to scratching.
85
How is nodular prurigo treated?
Topical corticosteroids or potent steroid ointments to reduce inflammation Emollients to improve skin barrier Antihistamines for itch relief Behavioral strategies to reduce scratching In severe cases, phototherapy or systemic treatments may be considered
86
What is the main principle in managing pruritus?
Identify the underlying cause (skin disorder or systemic disease) and treat it appropriately.
87
How is eczema / atopic dermatitis treated to relieve pruritus?
Soap substitutes to avoid irritation Emollients to restore skin barrier Topical corticosteroids for inflammation
88
How is scabies managed?
Topical benzyl benzoate (Ascabiol) for the patient Treat all household contacts simultaneously Wash bedding and clothes in hot water
89
How are papular urticaria and papular pruritic eruption (PPE) managed?
5% LPC / HEB applied at night Topical corticosteroids to active lesions Oral antihistamines for itch relief
90
How are fungal infections (tinea) managed?
Appropriate antifungal therapy — topical for localized, oral if extensive or scalp involvement
91
How is dry skin / xerosis managed?
Soap substitutes Regular use of emollients
92
What should be done if pruritus is due to a systemic cause?
Refer appropriately for management of underlying systemic disease (e.g., liver, kidney, thyroid, haematologic).
93
Mrs QP, a 54yo woman, presents with pruritus. There are no skin lesions. Which of the following is likely to be the most useful investigation? oTotal bilirubin oChest XRay oAST, ALT oSyphilis serology
oAST, ALT
94
A 16yo girl presents to you with pruritus. Which of the following is the most appropriate management? oReassure the patient and prescribe an antihistamine oAdvise the patient to use a topical corticosteroid on the itchy skin oExamine the patient to evaluate for the presence of a dermatological disorder oRecommend that the patient stops using any medication
oExamine the patient to evaluate for the presence of a
95
Which of the following would be a clue to a systemic cause of pruritus? oPale skin and mucous membranes oPatchy hair loss oLymphadenopathy oBurrows in web-spaces
oLymphadenopathy
Dermatology
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