Ichthyosis

Ichthyosis is a group of skin disorders marked by dry, thickened, scaly skin. It results from abnormal production or shedding of skin cells and ranges from mild to life-threatening.

Epidermis: The outermost layer of skin, forming a protective barrier and renewing through continual cell production. Ichthyosis disrupts the epidermis, where abnormal renewal or shedding creates visible scale.
Filaggrin: A protein that helps aggregate keratin filaments and contributes to natural moisturizing factors in the skin. Loss-of-function variants can cause ichthyosis vulgaris and impair the skin’s hydration barrier.
Ichthyosis vulgaris: A common inherited ichthyosis characterized by dry skin and fine scaling, often linked to filaggrin variants. This frequent, usually mild form shows how ichthyosis can overlap with common skin conditions.
Genetic testing: Laboratory analysis that identifies disease-associated changes in a person’s DNA. A gene result can confirm a suspected inherited subtype and clarify inheritance.
Psoriasis: A chronic immune-mediated disease that causes sharply demarcated plaques of thickened, inflamed skin. Inflammatory plaques distinguish psoriasis from the usually generalized scaling of ichthyosis.
Keratinocyte: The predominant cell of the epidermis, producing structural proteins and forming the skin barrier. Many forms involve altered keratinocyte development or movement toward the skin surface.
Transglutaminase 1: An enzyme that cross-links proteins to form the cornified envelope of epidermal cells. Its deficiency causes a major form of autosomal recessive congenital ichthyosis.
X-linked ichthyosis: An inherited scaling disorder usually caused by deficiency of steroid sulfatase, encoded on the X chromosome. Its inheritance and dark, adherent scales distinguish it from the more common vulgaris form.
Skin biopsy: A procedure that removes a small skin sample for microscopic examination. Histology can help distinguish ichthyosis patterns when clinical findings are unclear.
Atopic dermatitis: A chronic inflammatory skin disease characterized by itchy, relapsing eczema and a weakened skin barrier. Its episodic itchy inflammation differs from the persistent scale typical of ichthyosis.

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