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.