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Skin psoriasis, a multi- causal disease with unknown mechanism, has several clinical aspects. Besides ordinary psoriasis with mica-like plaques and its special locations, two less known notions are underlined: the localized forms are often less typical (for example: scalp, ears, folds of the hand, foot and nails). They may be relevant to the rhumatologist for the diagnosis the inflammatory forms are often disseminated with pustules and keratosis and constitute another groups where the rhumatologic manifestations are more frequent and more severe. Various forms of treatment are active on the cutaneous symptoms, chronic or relapsing topical therapy with tar, corticoids, nitrogen mustard, photochemytherapy, oral derivatives of retinoic acid, and exceptionally immunosuppressors. Each technic has its advantages, its disadvantages on a short or long term. Therefore each patient should receive the therapy which is adapted to his form of psoriasis, the need and possibilities of the patient. Collaboration is a must and each patient should receive the adequate care making possible an improvement of his condition.

The carcinogenic risk of photochemotherapy (PUVA) with bi-functional furocoumarins such as 8-methoxypsoralen (8-MOP) which form cross-links in cellular DNA has initiated a search for active but less hazardous psoralens. A new compound, 3-carbethoxypsoralen (3-CPs), studied in the yeast Saccharomyces cerevisiae (eukaryote), has been shown to be very photoactive on DNA and to form only mono-additions to DNA. These lesions appear to be more easily repaired than the cross-links induced by 8-MOP. 3-CPs produces less nuclear genetic events such as nuclear mutations and mitotic crossovers, but more cytoplasmic 'petite' mutations (damage to mitochondrial DNA) than 8-MOP. In mice it was demonstrated that after local or intra-peritoneal administration, in contrast to 8-MOP, 3-CPs is non-toxic, non-erythematogenic, and non-carcinogenic. A study of ten psoriatic patients had shown that local applications of 3-CPs plus UV-A exhibit about the same therapeutic activity for the clearing of psoriatic lesions as local treatment with 8-MOP plus UV-A, but without any localized hyperpigmentation.

The possible role of epidermal serine proteases in the genesis of psoriatic lesions was investigated by sequential biopsies of the epidermal damage induced by topical cantharidin. In the skin of normal subjects, epidermal damage was followed by the transient appearance of proteolytic activity in the upper epidermis accompanied by temporary hyperacanthosis and perivascular inflammatory cells in the superficial dermis. In the uninvolved skin of five patients with psoriasis this proteolysis persisted longer, for more than 7 days. Thereafter, in three of the patients, the proteolysis abated, and this was followed by disappearance of the hyperacanthosis and the dermal infiltrate; in the other two psoriatics the proteolysis and hyperacanthosis increased, and a typical Koebner phenomenon ensued. Migration of neutrophils into the epidermis occurred as a later event. Thus the abnormal persistence of proteolytic activity in the upper epidermis after cantharidin application distinguishes the normal from the psoriatic skin injury response and might initiate the psoriatic lesion.

Extensive lesions on 36 patients with psoriasis were treated by Tigason, I mg/kg/day plus PUVA until skin clearance. A clinical score was calculated for each body area, and erythema, scaling, thickness and pruritus of the lesions were scored from 0 to 3. Skin clearing was defined as a clinical score less than 10% of the initial score. Double-blind maintenance treatment was then started. This was Tigason at half of the maximal dose tolerated during the clearing phase of the treatment v. placebo. Relapse of the disease was defined as the occurrence of a clinical score greater than 50% of the initial score. Among the 36 patients randomized, 20 received placebo and 16 received Tigason. Relapses increased quickly in the patients on placebo, but occurred in few patients treated by Tigason with 60% remaining clear after 1 year (P less than 0.05). Surprisingly, the kinetics of disappearance of the most frequent side effect, cheilitis, was the same in the Tigason group and in the placebo group. This double-blind randomized clinical trial shows that Tigason at low doses is an efficient and well-tolerated maintenance treatment of psoriasis.

A reproducible method for sequential study of migration out of human skin, phagocytosis and bactericidal activity of neutrophils is described. Untreated psoriatics exhibit an early increase of chemotactic activity (0-8 hr, p less than 0.02) and subsequently a strong inhibition of chemotaxis (8-24 hr, p less than 0.01), a slight decrease of phagocytosis and a decrease in bactericidal activity (20 min, p less than 0.02; 30 min, p less than 0.003); 60 min, p less than 0.001; 120 min, p less than 0.001) as compared with controls. After clearing of skin lesions, the early increased chemotactic activity returned to normal values but the subsequent chemotactic inhibition remains as strong as before treatment. Phagocytosis increased to normal values (p less than 0.02) and bactericidal activity also increased but remained significantly low. These abnormalities were more evident in migrating than in circulating neutrophils, underlining the sensitivity of the described method.

Presents letters to the editor regarding articles published in the previous issues of the "British Journal of Dermatology." "Lichen sclerosus et atrophicus in non-identical female twins," which discusses the development of perineal lichen sclerosus et atrophicus in female twins; "Influence of containers on the quantities of topical preparations used," which was about the dispensing of topical agents; "Laser, dermal fibroblasts and psoriasis," which was about psoriasis.