Pruritus

Question 1

Give some examples of broad classes of pruritogenic mediators?

Answer 1

Proteases, lipid mediators, neuropeptides, opioids, cytokines (Metz et al. Vet Derm. 2013)

Question 2

What are some topical agents for treatment of pruritus?

Answer 2

Capsaiscin, calcineurin inhibitors (tacrolimus and pimecrolimus), and cannabinoid agonists (N-palmitoyl ethanol amine. (Metz et al. Vet Derm. 2013)

Question 3

What are some systemic therapies for pruritus?

Answer 3

Antihistamines, anticonvulsants, opiate receptor antagonist or agonists, antidepressants, ciclosporin, and UV light. (Metz et al. Vet Derm. 2013)

Question 4

For how long must itch persist for it to be considered chronic pruritus?

Answer 4

More than six weeks (Metz et al. Vet Derm. 2013)

Question 5

What is the function of pruritus

Answer 5

Serves as an alarm system to effectively remove damaging or harmful substances on the skin (Metz et al. Vet Derm. 2013)

Question 6

How is pruritus mediated in the skin?

Answer 6

Pruritus is mediated by free nerve endings of non-myelinated nerve fibers that are located at the dermoepidermal Junction and within the epidermis (Metz et al. Vet Derm. 2013)

Question 7

How do physical stimuli, such as cold and heat, modulate the perception of itching?

Answer 7

Painful heat and cold can significantly diminish itching, while moderate cold intensifies it. (Metz et al. Vet Derm. 2013)

Question 8

A sub population of Pruritus-specific non-myelinated C fibers exist that respond only to_________

Answer 8

A sub population of Pruritus-specific non-myelinated C fibers exist that respond only to histamine. (Metz et al. Vet Derm. 2013)

Question 9

What is the gastrin releasing peptide receptor?

Answer 9

A specific receptor in the posterior spinal cord in mice which is exclusively responsible for transmitting the perception of pruritus but not pain or temperature perception

Question 10

True or false: Pruritus can arise peripherally and then be transmitted to the CNS, but cannot originate in the CNS or spinal cord

Answer 10

False. Pruritus can arise peripherally and then be transmitted to the CNS, or it can originate in the CNS or spinal cord(Metz et al. Vet Derm. 2013)

Question 11

Intrathecal administration of which substances has been shown to cause scratching, biting and other pruritus related reactions?

Answer 11

Vasoactive intestinal polypeptide, calcitonin gene related peptide, substance P or opioids (Metz et al. Vet Derm. 2013)

Question 12

What is the gate control theory?

Answer 12

Pruritus is suppressed by mechanical or electrical stimulation of rapid transmitting myelinated A-fibers at the spinal level in favor of transmitting pain sensation. This explains the anti-pruritic effects of scratching. (Metz et al. Vet Derm. 2013)

Question 13

In mast cells, is histamine preformed or produced following stimulation?

Answer 13

Preformed in large amounts. (Metz et al. Vet Derm. 2013)

Question 14

Which receptors does histamine stimulate to induce pruritus?

Answer 14

H1 receptors (Metz et al. Vet Derm. 2013)

Question 15

Which lipid mediators may be involved in pruritus?

Answer 15

Leukotriene B4, Protstaglandin D2, and prostaglandin E2. (Metz et al. Vet Derm. 2013)

Question 16

Which neuropeptides are the most important mast cell activators?

Answer 16

Vasoactive intestinal polypeptide, calcitonin gene-related peptide and substance P. (Metz et al. Vet Derm. 2013)

Question 17

The activation of which opioid receptor causes pruritus? The activation of which opioid receptor inhibits pruritus?

Answer 17

µ-receptor causes pruritus. 𝛋-receptor inhibits pruritus. (Metz et al. Vet Derm. 2013)

Question 18

Which interleukins have been associated with pruritus?

Answer 18

IL-2, IL-6, IL-8, and IL-31 (Metz et al. Vet Derm. 2013)

Question 19

In terms of chronic pruritus, describe the process of peripheral sensitization.

Answer 19

Chronic stimulation of neuroreceptors, such as histamine or capsaicin receptor (TRPV1), bu inflammatory mediators such as bradykinin, prostaglandins and neurotrophins ultimately leads to reduction of stimulus threshold of these receptors. (Metz et al. Vet Derm. 2013)

Question 20

What is allokinesis?

Answer 20

Itching triggered by normal non-pruritogenic stimulus. (Metz et al. Vet Derm. 2013)

Question 21

What are the secondary reactive changes to chronic scratching called? What do they look like?

Answer 21

Lichen simplex chronicus, lichen amyloidosus, or prurigo nodularis.

Appears as flat or papular lichenification with hyper or depigmentation and scar formation. Can eventually appear as red or hyper pigmented papule, plaques or nodes.
(Metz et al. Vet Derm. 2013)

Question 22

What are the four types of etiological classifications of pruritus?

Answer 22

Pruriceptive pruritus, neuropathic pruritus, neurogenic pruritus, and psychogenic pruritus (Metz et al. Vet Derm. 2013)

Question 23

What is pruriceptive pruritus? Give some examples of causes.

Answer 23

Transmitted through C-fibers, originates directly in the skin, for example, as a consequence of dermatoses, such as psoriasis or excitation eczema. (Metz et al. Vet Derm. 2013)

Question 24

What is Neuropathic pruritus? Give some examples.

Answer 24

Caused by damage of the itch-transmitting afferents of the peripheral nerves or the spinal cord. Brachioradial pruritus, post-herpetic pruritus and nostalgia paraesthetica. (Metz et al. Vet Derm. 2013)

Question 25

What is neurogenic pruritus? Give some examples.

Answer 25

Caused directly by diseases of central structures of the CNS. Brain tumors, abscesses. (Metz et al. Vet Derm. 2013)

Question 26

What is psychogenic pruritus?

Answer 26

Based on metabolic disorders in the CNS. Tactile hallucinations, delusional state of parasitosis. (Metz et al. Vet Derm. 2013)

Question 27

What is pruritus of primarily noninflamed skin? What did this used to be called?

Answer 27

Generalized or localized pruritus without initial occurrence of skin changes. Used to be called pruritus sine material. (Metz et al. Vet Derm. 2013)

Question 28

What is pruritus of primarily inflamed skin?

Answer 28

Pruritus occurring with an inflammatory skin disease (dermatosis, cutaneous lymphoma, leukemic infiltrates, etc). (Metz et al. Vet Derm. 2013)

Question 29

What are some systemic diseases leading to pruritus?

Answer 29

CHolestatic liver disease, chronic renal insufficiency, DM, iron deficiency and hematological pruritus, as well as sold neoplasms and lymphoma. (Metz et al. Vet Derm. 2013)

Question 30

What types of dermatoses can induce chronic pruritus?

Answer 30

Inflammatory diseases - atopy, psoriasis, urticaria
Infectious diseases - mycotic, bacteria, viral, scabies, pediculosis, insect bites, folliculitis
Autoimmune - bullous dermatoses (dermatitis herpetiformis [Duhring’s disease], bullous pemphigoid)
Neoplstic - T-cell lymphoma. (Metz et al. Vet Derm. 2013)

Question 31

What is the most common type of physical urticaria? In which species has it been described?

Answer 31

Dermographic urticaria. Described in horses, dogs, and cows. (Metz et al. Vet Derm. 2013)

Question 32

What 3 types of physical urticaria have been described?

Answer 32

Dermographic urticaria, cold urticaria, and cholinergic urticaria. (Metz et al. Vet Derm. 2013)

Question 33

In which species is chronic urticaria most commonly observed?

Answer 33

Horses. (Metz et al. Vet Derm. 2013)