Sx

Pruritic Condition

search

Pruritic Condition, Pruritus, Itch

  • Definition
  • Pruritus
  1. Unpleasant cutaneous sensation provoking scratching
  2. Itch
  • Epidemiology
  1. Very common in elderly patients
  • Pathophysiology
  1. Nerve fiber involvement
    1. Origin of itch is within skin free nerve endings
      1. Fibers most concentrated in wrists and ankles
      2. Unmyelinated C fibers to dorsal horn in spinal cord
    2. Scratching is a spinal reflex response
    3. Ascends to cerebral cortex via Spinothalamic Tract
  2. Chemical mediators
    1. Substance P
    2. Opioid and nonopioid peptides
    3. Somatostatin
    4. Neurokinin A
    5. Histamine
    6. Serotonin
    7. Prostaglandins
  3. External mediators
    1. Skin inflammation
    2. Environmental heat or dryness
    3. Vasodilation
    4. Psychological concerns
  • Causes
  • Evaluation
  1. Identify primary Dermatologic Causes of Pruritus
    1. Atopic Dermatitis: Atopy, Asthma, or Urticaria
    2. Contagious contacts (Pediculosis or Scabies)
    3. Consider Localized Causes of Pruritus
    4. Consider Timing (Xerotic Eczema worse in winter)
  2. Identify potential exposures
    1. See Environmental Causes of Pruritus
    2. See Medication Causes of Pruritus
  3. Review mental health concerns (e.g. Major Depression)
  4. Consider Systemic Causes of Pruritus
    1. Observe for cholestasis (e.g. Jaundice, Hepatomegaly)
    2. Observe for Lymphadenopathy
    3. Observe for thyromegaly
  • Labs
  • Systemic Cause Evaluation
  1. Approach
    1. Base lab testing on history and physical
    2. Avoid broad shotgun approach to lab testing
  2. Dermatologic Cause Evaluation
    1. Skin Scrapings for Scabies and Dermatophytosis
    2. Skin biopsy
      1. Mastocytosis
      2. Mycosis Fungoides
      3. Autoimmune Bullous Disease
  3. Systemic Cause Evaluation
    1. Thyroid Function Test (evaluate for Hyperthyroidism)
    2. HIV Test for high risk behaviors
    3. Liver Function Tests (evaluate for cholestasis)
      1. Serum Bilirubin
      2. Alkaline Phosphatase
    4. Hematologic tests
      1. Serum Ferritin
      2. Blood Urea Nitrogen (BUN)
      3. Complete Blood Count (CBC)
      4. Calcium
      5. Albumin
  • Radiology
  • Systemic Cause Evaluation
  1. Chest XRay (if Lymphoma suspected)
  2. Right upper quadrant Ultrasound (for cholestasis)
  • Complications of persistent scratching
  1. Bacterial superinfection
  2. Lichen Simplex Chronicus
    1. Thickened skin in response to repeated scratching