PRURITUS 2

Pruritusis an unpleasant sensation that provokes the desire to itch or scratch. 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 its own-right.  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 INTRODUCTION

PATHOPHYSIOLOGY OF PRURITUS Epidermis or DEJ (Nerve endings) Spino-thalamic Tract (C fibers) Thalamus Cerebral Cortex 4  are believed to lie either within the epidermis or very close to dermo-epidermal junction.  Itch nerve endings are believed to lie either within the epidermis or very close to dermo-epidermal junction.  Itching sensation is transmitted via (slow conduction speed) through spino-thalamic tract to the thalamus and on to a cortical representation.  Itching sensation is transmitted via C fibers (slow conduction speed) through spino-thalamic tract to the thalamus and on to a cortical representation.

CAUSES OF PRURITUS 5 PRURITUS Group I Generalized pruritus associated with skin disease Group II Localized pruritus associated with skin disease 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 LP 6. Generalized DH 7. Drug eruption (some cases) 6

II. SKIN DISEASES WITH LOCALIZED PRURITUS Common body sites affected by localized pruritus are: 1. Vulva [Pruritus vulvae] 2. Anal region [Pruritus ani] 3. Perineum 4. Scalp 5. External ear canal Common causes of localized pruritus are: 1. Eczema (especially LSC and nummular eczema) 2. LP 3. DH 4. Pediculosis 7

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. 8

SYSTEMIC CAUSES OF PRURITUS 1. Liver disease: Pruritus signals biliary obstruction (Cholestasis). The severity of itching usually correlates with the level of bilirubin.  Primary Biliary Cirrhosis (Itching is an early feature)  Viral Hepatitis (HBV & HCV) Mechanism of itching :-Cholestasis (1) Elevated bile salts (irritant to the nerve endings) (2) Central opioid effect Hepatitis C: unknown mechanism, probably due to biliary obstruction Treatment: Colestyramine/ Rifampicin/ Antihistamines/ UVB/ Naloxone Colysteramine often helps cholestatic pruritus probably through promoting elimination of bile salts i.e. chelating effect. Naloxone is an opioid antagonist. 9

2. Chronic Renal Disease  Itching occurs in CRF but not in ARF.  As high as 1/3 of patients undergo dialysis may complain generalized pruritus. Mechanism of itching : is unknown as blood urea level seems not to be responsible for itching. Multifactorial mechanism including secondary hyperparathyroidism and elevated plasma histamine has been suggested. Treatment :  UVB  Oral activated charcoal  Capsiacin 10 SYSTEMIC CAUSES OF PRURITUS

3. Blood Disease A. Iron deficiency anaemia: Itching may occur in severe cases with low Hb level. Correction of Hb level with iron replacement usually alleviate or abolish itching. B. Polycythaemia rubra vera: itching is usually triggered by a hot bath with a curious pricking sensation that usually lasts about an hour. C. Leukaemia: Itching occurs in all types of Leukaemia but more commonly in CLL. D. Lymphoma E. Myeloma Mechanism of itching in hematological diseases is unknown except in Iron deficiency anaemia in which it is due to iron deficiency. 11

4. Endocrine Disease 1- Thyroid Disease (Hyperthyroidism & Hypothyroidism): Generalized itching is due to dry skin (Xerosis). Emollients may help itching. Generalized itching is due to dry skin (Xerosis). Emollients may help itching. 2- Diabetes mellitus: Itching rarely occurs in diabetics and it may be due to skin xerosis. Itching rarely occurs in diabetics and it may be due to skin xerosis. 3- Pregnancy: Itching may occur in 3 rd trimester. The mechanism of pruritus is unknown, however it may be due to Obstructive Cholestasis usually associated with abnormal liver function tests. Biliary stasis in pregnancy is usually subclinical. Treatment: Emollients/ Chlorpheniramine/ Colestyramine/ Early delivery. Treatment: Emollients/ Chlorpheniramine/ Colestyramine/ Early delivery. 12

5. Malignancy A. Hodgkin’s disease: itching may occur in as high as 30% of the patients. It may be unbearable and may precede other manifestations of this disease by a longtime. B. Mycosis fungoides C. Carcinoma: Ca Breast, Bronchus, Stomach & Pancreas may rarely cause generalized itching. The Mechanism of itching is unknown and there is no successful therapy to control or reduce itching. 13

6. Infections A. HIV Infection: Itching may be caused by some opportunistic infections in HIV-infected person. However, itching may be encountered in HIV-infected individuals for unknown reason. Itching may be caused by some opportunistic infections in HIV-infected person. However, itching may be encountered in HIV-infected individuals for unknown reason. Treatment is directed toward these opportunistic infections, otherwise UVB may provide some help in cases with unknown reason. Treatment is directed toward these opportunistic infections, otherwise UVB may provide some help in cases with unknown reason. B. Worm infestations: Rarely itching may be due to Hydatid disease, Ascariasis or Ancylostomiasis. Rarely itching may be due to Hydatid disease, Ascariasis or Ancylostomiasis. 14

7. Psychogenic Pruritus Usually there is no underlying organic cause and the skin is normally looking on examination. The diagnosis is made after excluding all other possible causes. Mechanism of itching: Unknown TreatmentPsychotherapyAnxiolyticsAntidepressives 15

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: 1. GUE 2. GSE 3. CBC and ESR {Low ESR in Polycythaemia rubra vera} 4. Blood chemistry: FBS/ B. Urea/ TSB/ RFT/ LFT and Thyroid FT. 5. Chest Radiograph 6. More sophisticated Investigations accordingly (US/ CT Scan/ Barium studies/ MRI …etc.) 16

TREATMENT Treat or correct any primary underlying cause, otherwise try to give symptomatic treatment to alleviate itching. Treat or correct any primary underlying cause, otherwise try to give symptomatic treatment to alleviate itching. 1. Local therapies to decrease itching include:  Emollients (lubricate the skin)  Calamine lotion  Topical menthol (1%)  Capsaicin  Topical CS (have potent anti-pruritic effect) 17

2. Phototherapy: UVB and PUVA 3. Systemic therapies:  Systemic H1 blocking Antihistamines  Opioid antagonists such as Naltrexone/ Naloxone  Systemic Cs (Short course small dose) 18