1. PRURITUS
Dr Sami Billal
MSc,MD

2. 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.

3. 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.

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

5. 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

6. I. SKIN DISEASES WITH GENERALIZED PRURITUS

7. 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)

8. II. SKIN DISEASES WITH LOCALIZED PRURITUS

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

10. Common causes of localized pruritus are:
Eczema LP DH
Pediculosis

11. III. PRURITUS WITH NO EVIDENCE OF SKIN DISEASE

12. 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.

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

14. 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)

15. 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:

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