Pruritus, generalised Flashcards
Probability diagnosis
- Psychological/emotional
- Old, dry skin (senile pruritus)
- Atopic dermatitis (eczema)
- Contact (allergic) dermatitis
- Varicella (chicken pox)
The broad differential diagnoses are:
- skin disease
- systemic disease
- psychological and emotional disorders
Serious disorders not to be missed
Cancer:
- lymphoma/Hodgkin
- leukaemia: CLL
- multiple myeloma
- other cancer, e.g. mycosis fungoides
Scabies (severe infestation)
Chronic kidney failure
Primary biliary cirrhosis/other causes (e.g. jaundice)
Pitfalls (often missed)
Pregnancy
Tropical infection/infestation
Polycythaemia rubra vera
Polyarteritis nodosa
Lichen planus
Generalised sensitivity (e.g. fibreglass, bubble bath)
Masquerades checklist
Depression
Diabetes
Drugs (several types; see list)
Anaemia (iron deficiency)
Thyroid (hyper and hypo) disorders
Spinal dysfunction (nostalgia paraesthetica)
Is the patient trying to tell me something?
Quite likely: consider anxiety, parasitophobia.
Key history
Enquire about nature and distribution of itching.
Consider pregnancy, liver disease and malignancy of the lymphatic system, particularly Hodgkin lymphoma.
A careful review of any drug history is important.
Note any associated general symptoms such as fever.
Key examination
General examination of the skin
abdomen and
lymphopoietic systems
Key investigations
- Bloods;
- FBC
- ESR/CRP
- pregnancy test
- iron studies
- kidney function tests
- TFTs
- blood sugar
- LDH
Consider further investigations based on clinical suspicion, e.g.
- Urinalysis
- CXR
- Skin biopsy
- Stool examination (for ova and cysts)
- Lymph node biopsy (if present)
- Skin testing
Diagnostic tips
The itching of polycythaemia may be triggered by a hot bath and lasts for at least 1 hour.
Pruritus can be the presenting symptom of primary biliary cirrhosis and may precede other symptoms by 1–2 years.
The itch of Hodgkin lymphoma (in 30%) may be unbearable.
Drugs that can cause pruritus: aspirin, barbiturates, morphine, cocaine, penicillin, other antibiotics, anticytotoxics.
Treatment
- The basic principle is to determine the cause of the itch and treat it accordingly.
- Itch of psychogenic origin responds to appropriate therapy, such as antidepressants for depression.
- If no cause is found:
- apply cooling measures (e.g. air-conditioning, cool swims)
- avoid rough clothes
- avoid known irritants
- avoid overheating
- avoid vasodilatation (e.g. alcohol, hot baths/showers)
- treat dry skin with appropriate moisturisers (e.g. propylene glycol in aqueous cream)
- topical treatment:
- emollients to lubricate skin
- local soothing lotion such as calamine, inc. 0.5% menthol in cetomacrogol cream (or other emollient base if the patient prefers, applied liberally as often as needed – prescribe 3 × 500 g minimum), or Phenol (avoid topical antihistamines)
- pine tar preparations (e.g. Pinetarsol)
- crotamiton cream
- Consider these medications:
- topical corticosteroids – If unsuccessful after a few weeks regular use, potent topical corticosteroids are not indicated.
- Prednisone is not indicated for specific or nonspecific pruritus.
- Sedative antihistamines (not very effective for systemic pruritus). If used, give once daily at night, e.g. promethazine 10 to 75 mg, and use with caution in the elderly.
- Non-sedating antihistamines during day
- Antidepressants or tranquillisers (if psychological cause and counselling ineffective)
- tricyclic antidepressants – amitriptyline 10 to 75 mg. Start low and build up dose, particularly in older adults.
1. If an underlying cause is found, other medications may be helpful, e.g. gabapentin, pregabalin for renal pruritus, colestyramine, rifampicin for cholestatic pruritus. Seek appropriate specialist advice.
Request dermatology advice if:
- the above measures are unsuccessful after 2 months’ adequate trial.
- patients are severely distressed by their pruritus.
