Hyperkeratotic disorders

The topical and oral use of retinoids for treatment of hyperkeratotic disorders such as psoriasis and Darier s disease has long been established. Systemic retinoid therapy is often combined with topical diugs such as corticosteroids, dithranol, tar, and also UVA/UVB phototherapies where synergistic effects have been reported. 

Acitretin is most useful for the treatment of severe psoriasis, particularly the pustular and erythrodermic variants. Psoriatic nail changes and arthritis also may respond. Combining the drug with ultraviolet light therapy (Re-UVB, in the case of ultraviolet B radiation, or Re-PUVA, with psoralen plus ultraviolet A radiation) permits the use of lower doses of both acitretin and ultraviolet radiation. Other conditions for which the drug may be especially useful include congenital and acquired hyperkeratotic disorders, such as the ichthyoses and palmoplantar keratodermas, and severe lichen planus. 

For dermatological treatment the main focus has been on vitamins A and D. Retinoids have been used systemically and topically for the treatment of acne and a variety of hyperkeratotic disorders including psoriasis, ichthyoses, and lichenoid dermatoses as well as skin cancer.1 Vitamin D-analogs are of great importance for the topical treatment in psoriasis. 

A dramatic ( 75%) reduction in size and number of desmosomes was observed in a freeze-fracture analysis of keratinocyte membranes in patients with psoriasis treated with etretinate (Kitajima and Mori, 1983). This reduction in desmosomal size and number (Williams and Elias, 1981), which was particularly evident in the stratum comeum but also observed in the stratum spinosum of both lesional and nonlesional skin, appeared to be of sufficient magnitude to contribute significantly to the keratolytic effect of retinoids in hyperkeratotic disorders. Other factors, for example, decreased tonofrlaments and decreased glycocalyx cohesion, may also be contributory. This effect also has been observed in vitro as retinoids cause increased shedding of squames from stratified cultures of human foreskin epidermal cells (McGuire et al., 1982 Kubilus, 1980). 

Vitamin C (L-ascorbic acid Figure 37.41) can limit melanin production, as it has a tyrosinase-inhibiting and antioxidant activity. Skin cells naturally use ascorbic acid in energy metabolism and when synthesizing collagen. A deficiency in vitamin C is a well-known cause of many disorders, including hyperkeratotic folliculitis and delayed wound healing. 

Aids in the removai of excessive keratin in hyperkeratotic skin disorders, inciuding warts, psoriasis, caiiuses, and corns... 

Of the 488 former workers examined dermatologically, 115 had abnormal pigmentation and 22 had skin tumors of which 8 were cases of Bowen s disease (Inada et al. 1978). Pigmentation disorders were present in 57 cases of 109 engaged only in the production of mustard and in only 1 of 16 cases engaged only in the production of lewisite. Hyperkeratotic skin lesions such as Bowen s disease, basal cell carcinomas, and hyperkeratotic papular eruptions were present in 14 cases of 109 engaged only in mustard production and in 1 case of 16 engaged only in lewisite production. No abnormalities were observed in 77 for-... 

Hayakawa R (1996) Friction melanosis. In van der Valk P, Maibach HI (eds) The irritant contact dermatitis syndrome. CRC Press, Boca Raton, pp 213-220 Hersle K, Mobacken H (1982) Hyperkeratotic dermatitis of the palms. Br J Dermatol 107 195-202 Hogan DJ, Lane P (1986) Dermatological disorders in agriculture. 

A deficiency wherein hyperkeratinization of epidermis and other epithelia occurs. The other metabolic defect is that encountered in Refsum s disease, an inherited neurological disorder biochemically characterized by accumulation of phytanic acid due to failure of tissue hydroxylases to initiate its degradation by a-hydroxylation. In this disease dry hyperkeratotic scaliness of the skin appears in variable degrees, reported to be at times sufficiently extreme to mimic ichthyosis. As in the ichthyoses, hyperkeratinization of other epithelia does not occur. 

Tay s syndrome is an autosomal recessive disorder characterized by congenital ichthyosiform erythroderma, pili torti and trichorrhexis nodosa, mental and growth retardation. After some months the erythroderma subsides and the hyperkeratotic scaling is confined to the face, trunk and extensor aspects of the limbs. The palms and soles are thickened. The child shows a progeria-like appearance. 

Symmetrical progressive erythrokeratodermia is an autosomal dominant disorder which starts at birth or during early childhood ". Erythemato-hyperkeratotic, sharply outlined areas, occasionally hyperpigmented, usually symmetrical, are present on the extensor surfaces of the limbs (Figure 15.2), buttocks and, occasionally, on the trunk and face. Patches and plaques are persistent and slowly progressive from the beginning. Palms and soles are... 

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