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Pruritus

Medicine > Gastrointestinal

Differential Diagnosis Schema 🧠

Dermatological Causes

  • Eczema (Atopic dermatitis): Chronic inflammatory skin condition with itchy, red, and dry skin.
  • Psoriasis: Characterized by red, scaly plaques typically on the extensor surfaces; pruritus varies.
  • Contact dermatitis: Pruritus triggered by exposure to allergens or irritants; presents with localized rash.
  • Urticaria: Raised, itchy welts (hives) that may be triggered by allergens, infections, or stress.
  • Scabies: Intensely itchy rash, particularly at night, caused by a mite infestation.
  • Lichen planus: Pruritic, purple, polygonal, flat-topped papules, often on the wrists and ankles.
  • Fungal infections (e.g., tinea): Itchy, erythematous patches with central clearing, commonly affecting the feet, groin, or scalp.
  • Drug reactions: Exanthematous rashes associated with pruritus following drug exposure.
  • Xerosis (dry skin): Common in the elderly, particularly in winter, leading to generalized pruritus.
  • Lichen simplex chronicus: Thickened, itchy skin resulting from chronic scratching or rubbing.

Systemic Causes

  • Chronic kidney disease: Uremic pruritus associated with renal failure, often generalized and worse at night.
  • Cholestasis: Pruritus due to bile salt accumulation, seen in liver disease and during pregnancy (intrahepatic cholestasis of pregnancy).
  • Hematological disorders: Iron deficiency anemia and polycythemia vera can cause generalized pruritus.
  • Thyroid disease: Hyperthyroidism and hypothyroidism can present with pruritus.
  • Diabetes mellitus: Poorly controlled diabetes can lead to pruritus, particularly in the genital and lower limb areas.
  • Malignancies: Pruritus can be a paraneoplastic symptom, particularly in lymphomas and leukemias.
  • HIV infection: Pruritus can be an early or late manifestation of HIV, often due to associated infections or xerosis.
  • Parasitic infestations: Helminthic infections like strongyloidiasis or schistosomiasis may cause pruritus.
  • Psychogenic pruritus: Associated with psychiatric conditions like depression, anxiety, or somatoform disorders.
  • Pregnancy: In addition to cholestasis, pruritus gravidarum (generalized itching during pregnancy) can occur.
  • Drug-induced: Medications like opioids, ACE inhibitors, or antimalarials can cause generalized pruritus.
  • Hyperparathyroidism: Can cause pruritus due to hypercalcemia and calcium deposition in the skin.

Key Points in History 🥼

Symptom Characteristics

  • Onset: Acute vs. chronic onset may help distinguish between dermatological vs. systemic causes.
  • Location: Localized pruritus suggests dermatological causes; generalized pruritus raises suspicion of systemic conditions.
  • Timing: Nocturnal pruritus is common in scabies and uremia.
  • Associated rash: The presence of a rash can help identify specific dermatological conditions.
  • Aggravating factors: Heat, stress, or contact with specific substances may exacerbate symptoms.
  • Relieving factors: Use of emollients, antihistamines, or avoiding certain triggers may provide relief.
  • Seasonal variation: Worsening in winter suggests xerosis or atopic dermatitis.
  • Contact history: Recent exposure to new personal care products, allergens, or close contact with infected individuals (e.g., scabies).

Background

  • Medical history: Chronic conditions such as kidney disease, liver disease, or thyroid disorders.
  • Medication history: Recent changes in medication that could be associated with pruritus.
  • Family history: Eczema, psoriasis, or other dermatological conditions may have a genetic component.
  • Social history: Substance use, particularly alcohol or drugs that may cause pruritus, and occupational exposures.
  • Travel history: Exposure to parasitic infections or other infectious agents in endemic areas.
  • Psychosocial factors: Stress or psychiatric conditions that may contribute to or exacerbate pruritus.
  • Allergy history: Known allergies, including food, drugs, or environmental allergens.
  • Dietary history: Nutritional deficiencies, particularly in iron or vitamins, may contribute to pruritus.
  • Pregnancy: Specific consideration for pruritus related to pregnancy, such as intrahepatic cholestasis of pregnancy.

Possible Investigations 🌡️

Laboratory Tests

  • Full blood count (FBC): To check for anemia or underlying infections.
  • Liver function tests (LFTs): To assess for cholestasis or other liver dysfunctions.
  • Renal function tests (U&E): To evaluate for uremia in chronic kidney disease.
  • Thyroid function tests: To check for hyperthyroidism or hypothyroidism as a cause of pruritus.
  • Blood glucose levels: To screen for diabetes mellitus.
  • Serum iron studies: To assess for iron deficiency anemia.
  • Vitamin B12 and folate levels: Deficiencies may contribute to pruritus.
  • Serology for infections: Screening for hepatitis, HIV, and other systemic infections that could cause pruritus.
  • Autoimmune screen: To assess for conditions like systemic lupus erythematosus or Sjögren’s syndrome.
  • Serum calcium and phosphate: To check for hyperparathyroidism.
  • Bile acids: Particularly in pregnant women with pruritus to assess for intrahepatic cholestasis of pregnancy.
  • Skin biopsy: May be required for atypical or persistent rashes to identify specific dermatological conditions.
  • Immunoglobulin levels: To assess for conditions like multiple myeloma or other gammopathies.
  • Urinalysis: To check for glycosuria in diabetes or proteinuria in kidney disease.
  • Serum tryptase: To assess for mastocytosis in cases of unexplained pruritus.
  • Allergy testing: To identify specific allergens if allergic contact dermatitis is suspected.
  • C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR): To assess for underlying inflammatory or infectious causes.
  • Antinuclear antibody (ANA): To screen for autoimmune conditions associated with pruritus.
  • Eosinophil count: Elevated in parasitic infections and some allergic conditions.

Imaging and Other Tests

  • Abdominal ultrasound: To assess for liver or biliary tract abnormalities.
  • Chest X-ray: To rule out lymphadenopathy or other signs of lymphoma, which may present with pruritus.
  • Pelvic ultrasound: Particularly in pregnant women with pruritus to assess for complications like cholestasis.
  • CT scan: If malignancy is suspected as a paraneoplastic cause of pruritus.
  • MRI: For detailed imaging if neurological causes are suspected.
  • Endoscopy: May be indicated if gastrointestinal causes are suspected, particularly in cholestasis.
  • Dermatoscopy: To examine skin lesions more closely if a dermatological cause is suspected.
  • Patch testing: To identify allergens in suspected contact dermatitis.
  • Bone marrow biopsy: In cases of suspected hematological malignancies like lymphoma or leukemia.
  • Electrocardiogram (ECG): To assess for systemic involvement if cardiovascular causes are suspected.
  • Nerve conduction studies: If pruritus is suspected to be neuropathic in origin.
  • Gallium scan: To identify areas of inflammation or infection that might be causing pruritus.
  • PET scan: For detailed imaging in cases of suspected paraneoplastic syndrome.

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Gastrointestinal