Retinoids in disorders of keratinization: their use in adults.

Hereditary disorders of keratinization may be a considerable handicap. Oral treatment with retinoids has been shown to be effective in many of these diseases. In the group of ichthyoses, the best results can be obtained in the various types of nonbullous congenital ichthyosis (erythrodermic autosomal recessive lamellar ichthyosis, nonerythrodermic autosomal recessive lamellar ichthyosis, autosomal dominant lamellar ichthyosis). It should be borne in mind, however, that retinoid therapy alone cannot lead to a complete response of these forms of ichthyosis and that this treatment cannot replace an appropriate topical treatment. During continuous treatment with etretinate a reduction of the dosis to 0.5 mg/kg is often necessary. Etretinate treatment of bullous congenital ichthyosiform erythroderma is more difficult, and it is advisable to begin with a low dosis of 0.25-0.5 mg/kg. The epidermolytic form of palmoplantar keratoderma is in our opinion no indication for retinoid treatment which seems to result inevitably in large erosions. Good or excellent results have been seen in other forms of palmoplantar keratoderma including mal de Meleda, Papillon-Lefèvre syndrome, erythrokeratodermia variabilis, verrucous epidermal nevi, Darier disease and pityriasis rubra pilaris. In patients with Darier disease it is wise to begin with a relatively low dosage of 0.5 mg/kg and to adjust the dosage to the further course of the disease. The same is true for the ichthyosis seen in the Netherton syndrome, which may be either a diffuse hyperkeratosis or ichthyosis linearis circumflexa. In view of the fact that any inherited keratinization disorder requires long-term treatment, the risk of bone toxicity should be carefully weighed against the benefit of this therapy. The results so far obtained indicate that the effect of etretin is comparable to that of etretinate in the treatment of inherited keratinization disorders. Intermittent therapy should be tried whenever possible. A combination therapy seems reasonable in pityriasis rubra pilaris of the adult type. We have seen good results by combination with PUVA treatment. Autosomal dominant ichthyosis vulgaris and X-linked recessive ichthyosis are inappropriate to treat with oral retinoid therapy because these diseases are too mild. Papillomatous epidermal nevi should also be excluded because they do not respond to the drug. Hailey-Hailey disease may even be worsened by this treatment. According to our experience, oral retinoid therapy has no effect in monilethrix.