What are the types of pruritus?

Types of Pruritus

Pruritus (itch) can be classified into several distinct types based on underlying causes, with the main categories being pruritus with associated dermatosis and pruritus without underlying dermatosis. 1

Basic Classification of Pruritus

1. Pruritus with associated underlying dermatosis

   • Occurs with visible skin conditions like eczema, psoriasis, or seborrheic dermatitis
   • Inflammatory causes account for approximately 60% of chronic pruritus cases 2

2. Pruritus with no underlying dermatosis

   • Secondary pruritus due to underlying systemic disorder
   • Generalized pruritus of unknown origin (GPUO) - accounts for about 8% of all pruritus cases 1

Etiological Classification of Pruritus

1. Inflammatory Pruritus

• Associated with primary skin conditions
• Caused by eczema, psoriasis, or seborrheic dermatitis 2
• Often presents with characteristic skin lesions

2. Neuropathic Pruritus

• Due to localized or generalized nerve dysregulation
• Includes conditions like postherpetic neuralgia and notalgia paresthetica 2
• Accounts for approximately 25% of chronic pruritus cases (alone or mixed etiology)

3. Systemic Disease-Related Pruritus

• Disorders of iron metabolism

  • Iron deficiency or iron overload can cause generalized pruritus 1

• Renal disease

  • Uremic pruritus in chronic kidney disease 1

• Hepatic disease

  • Especially cholestatic liver conditions 1

• Malignancy

  • Hematological malignancies (lymphoma)
  • Solid tumors 1, 3

• Hematological disorders

  • Polycythemia vera (often presents with aquagenic pruritus)
  • Other myeloproliferative disorders 1

• Infections

  • HIV, hepatitis viruses
  • Parasitic infections 1

• Endocrine disorders

  • Thyroid dysfunction
  • Diabetes 1, 3

• Neurological disorders

  • Small fiber neuropathy 1

4. Drug-Induced Pruritus

• Medication side effects
• Common with opioids, antibiotics, and newer immunotherapies 1, 3

5. Psychogenic Pruritus

• Associated with psychological and emotional factors
• Also called functional itch disorder 3

6. Age-Related Pruritus

• Pruritus of elderly skin 1

7. Pregnancy-Associated Pruritus

• Related to hormonal changes during pregnancy 1

Special Types of Pruritus

Generalized Pruritus Without Rash (GPWOR)

• May be the first sign of underlying systemic disease
• Requires thorough investigation including blood tests for iron deficiency, renal and liver function 1, 4

Aquagenic Pruritus

• Triggered by water contact
• Often associated with polycythemia vera 1

Chronic Pruritus of Unknown Origin (CPUO)

• Persists despite comprehensive diagnostic workup
• No identifiable underlying cause 3

Clinical Approach

When evaluating pruritus, particularly generalized pruritus without rash, consider:

1. Duration: Acute (<6 weeks) vs. chronic (>6 weeks) 1
2. Distribution: Localized (suggests neuropathic cause) vs. generalized (suggests systemic disease) 3
3. Associated symptoms: May point to specific underlying conditions
4. Medication review: Essential to identify drug-induced causes 4

Common Pitfalls to Avoid

• Failing to check iron status - iron deficiency is a common and treatable cause of generalized pruritus 1, 4
• Overlooking hematological disorders - blood film examination should complement CBC when hematological causes are suspected 4
• Neglecting medication review - drugs are frequent causes of pruritus 4
• Performing unnecessary malignancy screening without specific symptoms 4

Understanding the type of pruritus is crucial for directing appropriate investigations and management strategies to improve patient outcomes and quality of life.