Pruritis (Itching) — Diffuse

Diffuse Pruritis  —  Differential Diagnosis

Skin Lesions Noted

No Rash or Lesions

  • Allergy without hives
  • Dermatographism
  • Xerosis (Dry Skin)
  • Biliary Tract disorders
  • Hodgkin’s / Hematologic Cancers
  • Blood Dyscrasias
  • Uremia
  • Hyperthyroidism
  • Dermatomyositis
  • Neuro Diseases (rare)
  • Psychogenic

SUMMARY APPROACH  —  Itching WITH Rash

[see below for Itching W/O Rash]

1.  If the rash comes & goes, it’ll be Urticaria (even if you don’t see it at the visit)
  • If lesions are present, you see wheals (hives)
  • Maybe you just see erythematous flares
2.  If lesions are fixed & visible, consider distribution & morphology:
  • Bilateral (often symmetric) scales or vesicles → Atopic Dermatitis (Eczema)
  • Annular macules / patches with leading edge → T. corporis (Ringworm)
  • Yellowish-tan / Reddish-tan plaques with extreme recalcitrant symptoms, consider cutaneous Mastocytosis (Rare!!!  Send to Derm to confirm)
3.  Scattered papules & excoriations.  Think:
  • Spreading contiguously from pubis → Pubic Lice (seek nits & maculae ceruleae)
  • Homeless?  Check seams of clothes for Body Lice
  • Exposed areas only?  Probably Bug Bites (papules-in-a-row =  Bedbugs)
  • Follicular pattern (inflamed hair follicles) → Folliculitis (common!!!)
4.  None of above convincing?  Might be Scabies:
  • Sex / close contact 3 weeks prior to onset, or others in house infested
  • Lesions on fingers & in webs, flexor creases of wrists
  • Burrows are pathognomonic (but often absent)
  • Virtually always on genitals, buttocks, near areolas (women)
  • NOT on back or face
  • Consider transparent tape microscopy (see last picture)
  • Can offer therapeutic trial

 

SUMMARY APPROACH  —  Itching WITHOUT Rash

1.  Test for Dermatographism (stroke small area with tongue blade).

  • If a hive, even just itching, develops, treat with an H1 Blocker (loratadine, etc).
2.  Brief H&P seeking:
  • Proximal muscle weakness, violacious rash (face or hands) → ESR, ANA, Muscle Enzymes (CK, AST, LDH, Aldolase) for Dermatomyositis & refer to Rheum
  • Raynaud’s, arthralgias, skin changes of scleroderma → ANA for Scleroderma & refer to Rheum
  • Suspicious nodes → biopsy for Lymphoma
  • Splenomegaly → CBC, Abdominal CT for Lymphoma
  • Dry Skin → TSH; therapeutic trial of emollients
  • Disordered thinking, obsessions → refer to Psych (also r/o meth abuse)
3.  Suspect Allergy (without hives)
  • Empiric H1 Blocker (loratadine, etc).  If no help, try doxepin.
  • Seek possible causes from common allergens (consider avoidance trial)

If pruritis persists…….

4.  Basic Labs: CBC, Comprehensive Metabolic Panel, TSH, ESR.  Chest X-ray.
  • Seek Dx of Uremia, Hematologic Malignancy, Hyperthyroidism
  • If ↑ Alk. Phos. → Antimitochondrial Ab for Primary Biliary Cirrhosis
  • ↑ Globulin → SPEP for Multiple Myeloma
  • ESR very high → consider Multiple Myeloma, Dermatomyositis.  Consider chest & abdominal CTs for Lymphoma
  • Chest X-ray:  seek adenopathy for Lymphoma
5.  Still no clues:  Refer to Derm
  • Continue to follow for B-symptoms or lymphadenopathy (if they occur, repeat labs & get pan-CT)

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