A symptom in several rare hereditary syndromes - ichthyosis vulgaris; X-linked ichthyosis; lamellar ichthyosis (nonbullous congenital ichthyosiform erythroderma), epidermolytic hyperkeratosis (bullous congenital ichthyosiform erythroderma). Also occurs in several systemic disorders. Xeroderma, the mildest form is neither congenital nor associated with systemic disease. Characteristics - skin is dry, scaling, thick over widespread parts of the body.

• inherited, Refsum's syndrome (hereditary mental deficiency and spastic paralysis), Sjögren-Larrson syndrome, leprosy, hypothyroidism, AIDS