Approach to Itch Flashcards
What is pruritus?
Unpleasant sensation of itching
What is the main and most common chemical mediator of itch?
Histamine
What is the general mechanism of pruritus?
1) Itch sensation via afferent C-fibres
2) Up spinothalamic tract
3) Reach thalamus → somatosensory cortex
What are 3 examples of itch mediators which stimulate C-fibres?
Major:
1) Histamine
2) Tryptase
3) Cathepsin S
4) IL-31
Minor:
5) Substance P
6) PGE
7) μ-opioid receptor agonists
What are 5 presentations of primary dermatoses?
1) Macule/patch
2) Papule/plaque
3) Nodule/cyst
4) Vesicle/bulla
5) Petechiae/purpura
What are 5 presentations of secondary dermatoses?
1) Erosions/Excoriations
2) Ulcer/fissures
3) Crusting
4) Lichenification
5) Scars
What are 5 Ddx for pruritus without primary dermatosis?
1) Liver disorders (eg. biliary obstruction)
2) Renal disorders (eg. uraemia)
3) Benign haematological disorders (eg. lymphoma)
4) Endocrine disorders (eg. poorly controlled DM, thyroid disorders)
5) Infections (eg. HIV)
6) Pregnancy
7) Neuropsychiatric disorders
What is the difference between primary and secondary dermatoses?
Primary: develop as a direct result of the disease process
Secondary: evolve from primary lesions or develop as a consequence of the patient’s activities
What are key questions for Hx in px with pruritus with primary dermatosis?
1) Contact Hx
2) Recent hospitalisation
3) Worse at night
4) Localisation
5) Known allergies
6) New medications/vaccinations
7) Infective symptoms
8) New items in contact with skin
9) Family Hx
10) Allergic symptoms
What are key questions for Hx in px with pruritus without primary dermatosis?
1) Alcohol
2) Hepatitis?
3) Changes in stools/Abdo distension
4) Bleeding issues
5) Mentation issues
6) Changes in urine output
7) Haematuria/bubbly urine
8) SOB/LL swelling
9) Fever/night sweats
10) Unintentional LOW
11) Fatigue
12) Frequent infections
13) Bleeding symptoms
14) Any masses
What is the most likely diagnosis for a px with:
1) Pruritus without primary dermatosis
2) fever/night sweats
3) fatigue
4) frequent infections
5) bleeding symptoms
6) any masses
Lymphoma (eg. Hodgkin’s)
What is the most likely diagnosis for a px with:
1) Pruritus without primary dermatosis
2) Changes in urine output
3) Haematuria/bubbly urine
4) SOB/LL swelling
Chronic renal disease
What is the most likely diagnosis for a px with:
1) Pruritus without primary dermatosis
2) Alcohol hx
3) Known hepatitis carrier
4) Changes in stools/abdo distension
5) Bleeding issues
6) Mentation issues
Decompensated chronic liver disease
What is the most likely diagnosis for a px with:
1) Pruritus with primary dermatosis
2) Contact Hx
3) Recent hospitalisation
4) Itch worse at night
Scabies
What is the most likely diagnosis for a px with:
1) Pruritus with primary dermatosis
2) Maculopapular eruption
3) New medication/vax
4) Recent infection
5) Mucosal infection
Drug exanthem
