Pruritus is a relatively common symptom presenting to general practice, accounting for approximately 1% of consultations. A thorough history and careful examination are of paramount importance in trying to discover the underlying cause.
Dermatological or systemic
Chronic pruritus refers to itching that has been present for six weeks or more. The first issue is to determine whether the pruritus is dermatological or systemic in nature.
Typically, dermatological skin conditions will have cutaneous manifestations. However, this should not be relied on and it is worth remembering that the itch can precede the development of the rash by some time. Dermatological causes of pruritus tend to be more localised in nature and have a more acute history.
It is well documented that systemic disease can manifest with pruritic symptoms. Haematological diseases, such as lymphoma, myelodysplastic syndrome and polycythaemia rubra vera, are well known to cause symptoms of itching.
Upset to the endocrine or metabolic systems can result in chronic pruritus. Examples include chronic kidney disease, liver disease, hyperparathyroidism, hyper/hypothyroidism and iron deficiency anaemia, all of which are known to cause pruritus.
Infections, such as HIV and parasitosis, can also be responsible for chronic pruritus, as can neurological disease, such as MS and brain tumours. Often overlooked are psychiatric causes for chronic itching, such as depression, schizophrenia, affective disorders and eating disorders.
Pruritus is commonly experienced during pregnancy and may be due to either dermatological or systemic causes.
There is also an increased incidence of pruritus in elderly patients. This is probably a consequence of age-related physiological skin changes, in addition to general comorbidities and polypharmacy.
Medication is a significant cause of itching and it can be extremely difficult to isolate which drugs may be responsible. Some drugs, such as aspirin and penicillin, classically cause pruritus with a skin rash, but a multitude of pharmacological agents purely induce an itch (see box 1).
|Box 1: Drugs that may induce itch|
|Common culprits include
In approximately 10% of cases, the cause of pruritus is unknown.
History and examination
The history is the key to determining the aetiology of chronic pruritus. It is important to ask about recent skin changes or any new skin products that may have been used.
Systemic enquiry is important to rule out any symptoms such as weight loss, fever, sweats or emotional stresses.
The pattern of itching is also important. Pruritus secondary to chronic kidney disease is typically localised to the back, abdomen, head and arms; in cholestatic pruritus, it tends to affect the hands and feet.
Nocturnal symptoms usually suggest an organic cause, because somatoform itching does not typically wake the patient at night.
The itching may have specific triggers, such as exertion in cholinergic pruritus, or bathing in aquagenic pruritus. Generalised itch is more common in winter, especially in the elderly. Family history is of value in the assessment, especially in terms of dermatological or autoimmune disorders. Recent itching in family members may point to conditions such as scabies.
A comprehensive drug history, including any recent blood transfusions, is also of great importance.
A full external examination is vital. This should include the skin, nails, hair and anogenital regions. The spleen, kidneys and lymph nodes should also be palpated. Initial investigations should include FBC, U&E, LFT, TFT, glucose and iron studies.
|Box 2 Specific treatments for pruritus|
Treatment should be guided by the aetiology, but self-help is beneficial. Explain to patients that they should avoid anything that dries out the skin. Limiting hot drinks, spicy food and alcohol can help, as can reducing stress. Restricting baths to 20 minutes in lukewarm water, emollients and air-permeable clothing can all aid itch reduction. Some more specific treatments also worth considering are discussed in box 2.
- Dr Garner is a salaried GP in Worcester