PRURITUS Dr Sami Billal MSc,MD

Definition Pruritus is an unpleasant sensation that provokes the desire to itch or scratch. Pruritus is a symptom that may be caused by many conditions. It is not a disease by itself. Pruritus is the commonest dermatologic complaint encountered during daily clinical practice. Majority of pruritus cases are due to primary skin disease, however it may be due to systemic disease.

Itch nerve endings are believed to lie either within the epidermis or very close to dermo-epidermal junction. Itching sensation is transmitted via C fibers (slow conduction speed) through spino-thalamic tract to the thalamus and on to a cortical representation.

PATHOPHYSIOLOGY OF PRURITUS Epidermis or DEJ (Nerve endings) Spino-thalamic Tract (C fibers) Thalamus Cerebral Cortex

CAUSES OF PRURITUS PRURITUS Group I Group II Group III Generalized pruritus associated with skin disease Group II Localized pruritus associated with Group III Pruritus with no evidence of skin disease

I. SKIN DISEASES WITH GENERALIZED PRURITUS

The most common causes of an itchy rash are: 1. Widespread eczema (usually atopic) 2. Scabies 3. Urticaria 4. Senile pruritus (Xeroderma) 5. Acute eruptive Lichen Planus 6. Generalized Dermatitis Herpetiformis (DH) 7. Drug eruption (some cases)

II. SKIN DISEASES WITH LOCALIZED PRURITUS

Common body sites affected by localized pruritus are: Vulva [Pruritus vulvae] Anal region [Pruritus ani] Perineum Scalp External ear canal

Common causes of localized pruritus are: Eczema LP DH Pediculosis

III. PRURITUS WITH NO EVIDENCE OF SKIN DISEASE

Pruritus with no evidence of skin disease may be termed Pruritus of Unknown Origin. Most cases of pruritus with no evidence of skin disease are due to systemic causes.

Liver diseases Chronic renal failure Blood diseases Malignancies Hypo and hyperthyroidism Pregnancy Infections Psychogenic

Management The following investigations may be needed to reach the cause of itching in cases of Pruritus with no evidence of skin disease after taking full history and making thorough physical examination: Urinalysis General stool examination CBC and ESR {Low ESR in Polycythaemia rubra vera} Blood chemistry: FBS/ B. Urea/ RFT/ LFT and Thyroid FT. Chest Radiograph More sophisticated Investigations accordingly (US/ CT Scan/ Barium studies/ MRI)

1. Local therapies to decrease itching include: TREATMENT Treat or correct any primary underlying cause, otherwise try to give symptomatic treatment to alleviate itching. Emollients (lubricate the skin) Calamine lotion Topical menthol (1%) Capsaicin Topical corticosteroid (have potent anti-pruritic effect) 1. Local therapies to decrease itching include:

2. Phototherapy: UVB and PUVA Systemic H1 blocking Antihistamines Opioid antagonists such as Naloxone Systemic corticoid (Short course small dose) 3. Systemic therapies: