Keratinization diseases are conditions that develop when cells in the skin are forming a tough, horny tissue termed keratin as they progress upward through the layers of the epidermis of skin to the outer surface stratum corneum. Ichthyoses include several inherited diseases and symptoms of several systemic disorders. Darier's disease, also known as keratosis follicularis, is a rare hereditary condition characterized by papular growths. Palmoplantar keratoderma is a localized or disseminated disease of the horny layer of the extremities.

Alterations in cell division, defects in cell differentiation, or changes in exfoliation from the surface can lead to irregularities in the skin surface that are characterized by rough, scaly skin with hyperkeratosis. Keratoses may occur as an inherited condition due to an autosomal dominant gene, an acquired condition due to environmental trauma, or as an early manifestation in systemic disease conditions, such as leprosy [see Diagnostic Code: 6302 Leprosy (Hansen's disease)], hypothyroidism (see Diagnostic Code: 7903 Hypothyroidism), lymphoma, or acquired immunodeficiency syndrome (AIDS)(see Diagnostic Code: 6351 HIV - Related illness).

The appearance of dry, scaly skin that sometimes takes on the appearance of fish scales. Itching may also be associated with keratinizating conditions. In ichthyosis, the skin is dry and scaly, ranging from mild dryness to severe dryness, associated with flaking. Darier's disease is characterized by papular growths that unite to form plaques of various sizes on the scalp, face, neck, trunk, and axillae. Palmoplantar keratoderma affects the horny layer of the palms of the hands and soles of the feet.

Physical examination of the skin may be sufficient to diagnose the condition. Skin biopsy may be done to identify underlying conditions. Consultation with a dermatologist may be recommended to receive genetic counseling and guidance to required treatments.

Minimizing bathing may be helpful, and soaps should be used sparingly. Topical therapy may include the application of lotions or ointments that soften and soothe the skin, and may provide symptomatic relief for all forms of ichthyosis. An emollient, such as plain petrolatum, mineral oil, or lotions containing alpha-hydroxy acids, may help to hydrate the stratum corneum when applied twice daily, especially after a bath. If the condition is a result of an underlying systemic disease, the primary disease must be treated. The most effective therapy for most forms of keratinization disorders are oral synthetic retinoids, such as vitamin A derivatives. The lowest effective dosage should be used.

Dryness may range from mild to severe, with scales and flaking that can become disfiguring or scarred. Patients with some disorders of keratization may require long-term antibiotic therapy as long as scaling is present to prevent infection. Long-term treatment with oral retinoid medications, such as isotretinoin, has resulted in bony growths arising from the surface of a bone, and other long-term side effects.

None.

• 38 CFR 4.118 (a) For the purposes of this section, systemic therapy is treatment that is administered through any route (orally, injection, suppository, intranasally) other than the skin, and topical therapy is treatment that is administered through the skin.   

• 38 CFR 4.118 (b) Two or more skin conditions may be combined in accordance with 38 CFR 4.25 only if separate areas of skin are involved. If two or more skin conditions involve the same area of skin, then only the highest evaluation shall be used.