Ichthyosis vulgaris

  • Autosomal semi-dominant
  • Clinical presentation is highly variable
    • Severity based on gene “dose”
  • Loss-of-function mutations in the filaggrin gene (FLG)
    • FLG mutation leads to defective skin barrier
    • Role in cross-linking a protein (involucrin) and lipids (ceramides)
    • It breaks down to amino acid metabolites increase skin hydration (”natural moisturizing factor”)
    • Without fillagrin transepidermal water loss is increased, leading to xerosis due to barrier disruption
    • Increased risk for atopic dermatitis
  • Presents in childhood but not at birth
    • Improves with age
  • Clinical key: dirty plate-like scales on the extensor surfaces, pre-tibial and lateral lower legs in particular
    • Spares flexural surfaces (helps differentiate from autosomal recessive ichthyosis)
    • Hyperlinear palms +/- keratoderma (helps differentiate from X linked ichthyosis)
    • Can have hipohidrosis/heat intolerance
    • Seasonal