PRURITUS
2
INTRODUCTION
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
PATHOPHYSIOLOGY OF PRURITUS
Epidermis or DEJ (Nerve endings)
Spino-thalamic Tract (C fibers)
Thalamus
Cerebral Cortex
 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
CAUSES OF PRURITUS
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
5
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
SYSTEMIC CAUSES OF PRURITUS
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
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.
2- Diabetes mellitus:
Itching rarely occurs in diabetics and it may be due to
skin xerosis.
3- Pregnancy:
Itching may occur in 3rd 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.
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.
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.
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
Treatment
Psychotherapy
Anxiolytics
Antidepressives
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.
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
 Opioid
H1 blocking Antihistamines
antagonists such as Naltrexone/
Naloxone
 Systemic
Cs (Short course small dose)
18