From the Guidelines
The workup for pruritus should begin with a thorough history and physical examination, followed by initial investigations including a full blood count and ferritin levels to check for iron deficiency, as recommended by the British Association of Dermatologists' guidelines 1. The initial evaluation should also consider other potential causes of pruritus, such as liver disease, kidney disease, and malignancies.
- A comprehensive metabolic panel, liver function tests, and urinalysis should be included in the initial workup to screen for these conditions.
- Specific tests may be added based on clinical suspicion, such as serum IgE levels for allergic conditions or skin biopsy for dermatological disorders.
- For patients with suspected hematological involvement, initial investigations should include a full blood count, blood film, lactate dehydrogenase, and erythrocyte sedimentation rate, as recommended by the British Association of Dermatologists' guidelines 1.
- Patients with generalized pruritus associated with iron overload should have liver function tests considered, and those with suspected polycythaemia vera should have blood samples sent for JAK2 V617F mutation analysis and/or be referred to haematology 1. The workup for pruritus should be tailored to the individual patient's presentation and medical history, and may involve consultation with specialists such as dermatologists, hematologists, or oncologists.
- A detailed medication review should be conducted if medication-induced pruritus is suspected, and patients with localized pruritus may require skin scrapings for microscopic examination or patch testing for contact dermatitis.
- The British Association of Dermatologists' guidelines recommend a thorough history and physical examination to identify potential causes of pruritus, and suggest that full investigation to rule out malignancy is not routinely recommended, unless there are systemic symptoms of malignancy 1.
From the Research
Workup for Pruritus
The workup for pruritus involves a thorough evaluation to determine the underlying cause of the itching sensation.
- A thorough skin examination, including visualization of the finger webs, anogenital region, nails, and scalp, is essential 2.
- Primary skin lesions indicate diseased skin, and secondary lesions are reactive and result from skin manipulation, such as scratching 2.
- An initial evaluation for systemic causes may include:
- Complete blood count with differential
- Creatinine and blood urea nitrogen levels
- Liver function tests
- Iron studies
- Fasting glucose or A1C level
- Thyroid-stimulating hormone test 2
- Additional testing, including erythrocyte sedimentation rate, HIV screening, hepatitis serologies, and chest radiography, may also be appropriate based on the history and physical examination 2.
Systemic Causes
Systemic causes of pruritus can be categorized into inflammatory, neuropathic, or a combination of both 3.
- Inflammatory causes may include eczema, psoriasis, or seborrheic dermatitis 3.
- Neuropathic causes may include postherpetic neuralgia and notalgia paresthetica, and are typically due to localized or generalized nerve dysregulation 3.
- Other systemic causes may include uremic pruritus, cholestatic pruritus, medication-induced pruritus, and infectious etiologies such as tinea corporis and scabies 3.
Diagnostic Approach
When evaluating patients with chronic pruritus, a structured history and physical examination may help narrow down the number of potential differential diagnoses 4.
- A thorough history, review of symptoms, and laboratory evaluation should be performed, particularly for people with chronic pruritus lasting less than 1 year 3.
- Clinicians should consider the following tests: complete blood cell count, complete metabolic panel, and thyroid function testing to evaluate for hematologic malignancy, liver disease, kidney disease, or thyroid disease 3.
- In the absence of primary skin lesions, physicians should consider evaluation for malignancy in older patients with chronic generalized pruritus 2.
Special Considerations
Cutaneous pruritus can be classified into two categories based on its distribution: localized cutaneous pruritus and generalized cutaneous pruritus 5.
- Localized cutaneous pruritus is indicative of a neuropathic cause, whereas generalized cutaneous pruritus suggests underlying systemic disease(s), drug-induced itch, psychogenic itch, or chronic pruritus of unknown origin (CPUO) 5.
- Systemic diseases associated with cutaneous pruritus include disorders of iron metabolism, chronic kidney disease, chronic liver disease, endocrine/metabolic diseases, hematological disorders, and malignant solid tumors 5.