魚鱗癬(ichthyosis

魚鱗癬(ichthyosis

Background

Ichthyosis refers to a relatively uncommon group of skin disorders characterized by the presence of excessive amounts of dry surface scales. It is regarded as a disorder of keratinization or cornification, and it is due to abnormal epidermal differentiation or metabolism.

The ichthyosiform dermatoses may be classified according to clinical manifestations, genetic presentation,¹ and histologic findings. Inherited and acquired forms of ichthyosis have been described, and ocular alterations may occur in specific subtypes. Five distinct types of inherited ichthyosis are noted, as follows: ichthyosis vulgaris, lamellar ichthyosis, epidermolytic hyperkeratosis, congenital ichthyosiform erythroderma, and X-linked ichthyosis.

Pathophysiology

In ichthyosis vulgaris, dry skin and follicular accentuation (keratosis pilaris) usually appear at puberty. Scaling is most prominent over the trunk, abdomen, buttocks, and legs. The flexural areas, such as the antecubital fossa, are spared. An association may be present between ichthyosis vulgaris and atopic diseases because one third to one half of patients show features of atopic disease and a similar proportion have relatives with atopic disease. A reported 11.5% association is noted between atopic dermatitis and primary hereditary ichthyosis. Ichthyosis vulgaris typically produces no significant ocular findings; however, scaling may be present on the eyelid skin, which could lead to punctate epithelial keratitis and recurrent corneal erosion. Linkage analysis has identified an ichthyosis vulgaris locus on band 1q22.