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Probability diagnosis


Old, dry skin (senile pruritus)

Atopic dermatitis (eczema)

Contact (allergic) dermatitis

Varicella (chicken pox)

Serious disorders not to be missed


  • 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)


Tropical infection/infestation

Polycythaemia rubra vera

Polyarteritis nodosa

Lichen planus

Generalised sensitivity (e.g. fibreglass, bubble bath)

Masquerades checklist



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



  • urinalysis

  • pregnancy test

  • iron studies

  • kidney function tests

  • TFTs

  • blood sugar

  • chest X-ray

  • 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.

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