What is pruritis?

What is Pruritus?

Pruritus is defined as the sensation that is relieved by scratching the skin, commonly known as itching, and is a distressing symptom that significantly impairs quality of life similar to chronic pain. 1

Definition and Pathophysiology

• Pruritus is perhaps the most common presenting symptom in dermatology, affecting approximately 8% of all cases as generalized pruritus of unknown origin (GPUO) 1
• It occurs when somatosensory neurons that carry the sense of touch, pain, and itch are activated by tissue damage or inflammation 1
• Pain and itch sensations arise from activation of primary sensory neurons, but are transduced by distinct subpopulations of sensory neurons and spinal afferent pathways, though there may be "cross-talk" between these neuronal circuits 1
• Various centers within the central nervous system are implicated in chronic pruritus perception, including signal transducer and activator of transcription 3, lipocalin-2-mediated signaling in astrocytes, and GABA A receptor activation in the central nucleus of the amygdala 1

Classification of Pruritus

Pruritus can be classified into several categories:

1. Pruritus with associated underlying dermatosis 1
2. Pruritus with no underlying dermatosis:
   • Secondary pruritus due to underlying systemic disorder
   • Generalized pruritus of unknown origin (GPUO) 1

• Pruritus can be acute (<6 weeks) or chronic (>6 weeks) 1
• Secondary changes due to rubbing or excoriation may be present in both types 1

Common Causes of Generalized Pruritus Without Rash

• Pruritic skin diseases before rash development 1
• Disorders of iron metabolism (both deficiency and overload) 1
• Uremia and renal insufficiency 1, 2
• Hepatic disease, especially cholestasis 1, 3
• Malignancy (Hodgkin's lymphoma, polycythemia vera, solid tumors) 1, 3
• Hematological disorders 1
• Infection (including HIV) 1, 2
• Endocrine disease (thyroid disorders, diabetes) 1, 2
• Neurological disorders 1
• Psychological and emotional factors 1
• Adverse drug reactions (particularly opioid-induced pruritus) 1, 3
• Heart failure 1
• Pregnancy 1
• Pruritus of elderly skin 1
• Pruritus of unknown origin (GPUO) 1

Diagnostic Approach

• For generalized pruritus without rash, a thorough evaluation for systemic causes should include:

  • Complete blood count with differential 2, 4
  • Ferritin levels (iron studies) 1
  • Liver function tests (bilirubin, alkaline phosphatase) 2, 4
  • Renal function tests (creatinine, blood urea nitrogen) 2, 4
  • Thyroid-stimulating hormone 2, 4
  • Additional testing as indicated: HIV screening, hepatitis serologies, chest radiography 4

• Iron deficiency is a common cause of generalized pruritus, with studies showing that iron replacement can lead to complete cessation of pruritus shortly after treatment begins 1

Management Approaches

• General management includes:

  • Trigger avoidance 4
  • Liberal emollient use to prevent xerosis 2, 4
  • Limiting water exposure 4
  • Oral antihistamines 4, 5
  • Topical corticosteroids 4

• For specific causes:

  • Iron deficiency: iron replacement therapy 1
  • Neuropathic pruritus: anticonvulsants, topical capsaicin 5
  • Psychogenic pruritus: psychotropic drugs, psychological therapy 1
  • Systemic conditions: treat the underlying disease 3

• Refractory cases may require:

  • Topical calcineurin inhibitors (tacrolimus, pimecrolimus) 6, 5
  • Systemic therapies such as anticonvulsants, opiate receptor antagonists, antidepressants, or immunosuppressants 5, 7
  • UV light therapy 5, 7

Impact on Quality of Life

• Chronic pruritus significantly impairs quality of life, similar to chronic pain 1
• Psychological factors can trigger or worsen pruritus, including stress, emotional excitation, and cognitive factors 1
• A nursing program called "Coping with Itch" has shown improvements in itch-related coping, though not necessarily in itch intensity 1