🩺 Pruritus

Pruritus, or itching, is an unpleasant sensation that provokes the desire to scratch. It can be a primary skin disorder or a cutaneous manifestation of a systemic, neurological, or psychiatric disease. In the UK general practice setting, it is one of the most frequent dermatological complaints. When associated with a rash, the diagnosis is usually cutaneous; however, 'itch without a rash' mandates a thorough investigation for underlying systemic pathology such as biliary obstruction, chronic kidney disease, or haematological malignancy.

Distinguish between localized and generalized itch. Ask about the timing (nocturnal itch is characteristic of scabies), triggers (heat, water, contactants), and the impact on sleep and quality of life. Review the systems for weight loss, night sweats (lymphoma), or altered bowel habits. A detailed drug history is essential, as opioids, ACE inhibitors, and statins are known to trigger pruritus.

Perform a head-to-toe skin examination looking for primary lesions (vesicles, papules) versus secondary lesions (excoriations, lichenification, prurigo nodules) caused by scratching. Check the finger webs and wrists for scabies burrows. Look for systemic clues: jaundice (cholestasis), pallor (anaemia), or lymphadenopathy (lymphoma). Assess for signs of chronic liver disease (spider naevi, palmar erythema) or uraemia (uraemic frost).

Dermatological (Eczema, Psoriasis, Scabies, Lichen Planus, Bullous Pemphigoid), Systemic (Chronic Kidney Disease, Cholestasis, Iron Deficiency, Hyper/Hypothyroidism, Lymphoma, Polycythaemia Vera), and Psychogenic.

Unexplained weight loss, night sweats, palpable lymphadenopathy, new onset jaundice, and nocturnal itching that prevents sleep.

If no primary skin disease is evident, perform a 'pruritus screen': FBC (anaemia/polycythaemia/eosinophilia), U&Es (renal failure), LFTs (cholestasis), TFTs (thyroid dysfunction), Ferritin, and HbA1c. A Chest X-ray is vital to exclude mediastinal lymphadenopathy (Hodgkin’s lymphoma). Skin scrapings for microscopy are indicated if scabies is suspected. LDH and Urate may be useful in suspected myeloproliferative disorders.

Pruritus without a rash is a classic 'medical' presentation requiring a screen for malignancy or organ failure. Iron deficiency can cause itching even in the absence of anaemia. Aquagenic pruritus (itching after a hot bath) is highly suggestive of Polycythaemia Vera. In elderly patients, itch may simply be due to xerosis (dry skin) resulting from reduced sebum production.

Aligned with 'Itch' and 'Chronic Skin Conditions'. Students must prioritize excluding occult malignancy and systemic organ failure when no rash is present. Knowledge of sedative vs. non-sedative antihistamines is required.