Xerosis

• Pathophysiology
  • Also known as xerosis cutis or asteatosis; refers to abnormally dry skin.
  • Caused by a defect in the epidermal barrier function leading to ↑ transepidermal water loss (TEWL).
  • Exacerbated by low humidity (winter), harsh soaps, and frequent hot bathing, which strip natural lipids from the stratum corneum.
  • Common in elderly pts due to age-related ↓ in sebaceous and sweat gland function.
• Clinical Features
  • Dry, rough, and scaly skin, often with fine flakes or cracks.
  • Pruritus is the dominant symptom and can be severe.
  • Common locations: Shins (most frequent), arms, hands, and trunk.
  • Spares areas with high sebaceous gland concentration (e.g., face, axilla, groin).

Feature	Xerosis	Eczema (Atopic Dermatitis)
Pathophysiology	Simple barrier dysfunction (↓ water)	Immune dysregulation (Th2, filaggrin)
Hallmark Symptom	Skin tightness, mild pruritus	INTENSE pruritus (“the itch that rashes”)
Key Sign	Fine scaling, “cracked” appearance	Lichenification (chronic), vesicles (acute)
Distribution	Generalized, esp. anterior shins	Flexural areas (antecubital/popliteal fossae)
Tx Foundation	Emollients	Emollients + Topical Corticosteroids for flares

• High-Yield Associations (Systemic Causes of Xerosis/Pruritus)
  • Hypothyroidism: Dry, coarse, cool skin.
  • Chronic Kidney Disease: Uremic pruritus.
  • Cholestatic Liver Disease: Due to bile salt deposition in the skin.
  • Malignancy: Especially Hodgkin lymphoma.
  • Nutritional Deficiencies: Vitamin A (phrynoderma), zinc.
  • Medications: Diuretics, retinoids.
  • Genetic Disorders: Ichthyosis vulgaris.
• Treatment
  • First-line: Liberal use of thick moisturizers (emollients), especially those containing ceramides, urea, or lactic acid.
    • Apply immediately after bathing on damp skin to trap moisture (“soak and seal”).
  • Lifestyle Modifications:
    • Use lukewarm water for short baths/showers.
    • Use mild, pH-neutral, non-soap cleansers.
    • Increase ambient humidity with a humidifier.
  • Second-line (for significant inflammation): Low-potency topical corticosteroids (e.g., hydrocortisone).
• Complications
  • Asteatotic eczema (Eczema craquelé): Inflammation and fissuring develop on xerotic skin, resembling “cracked porcelain.”
  • Secondary bacterial infection (impetiginization) from scratching, typically with S. aureus.