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Related diseases sometimes associated with psoriasis

5.1. Seborrheic dermatitis (photos 101 and 102)

Photo 101. Photo 102. Much more common than psoriasis (affecting 10% of the population), seborrheic dermatitis is often associated with it. Its preferred sites are the body’s median areas where the activity of the sebaceous glands is important: scalp, mediofacial region (photo 103), external auditory canal, mid-thoracic region, genital area and gluteal fold, but it can affect the whole body. It shows up in the form of erythematosquamous plaques, albeit far more superficial than those in psoriasis: erythema is pinkish and the squamae furfuraceous (or branny). The repercussion on the quality of life is usually connected with the visibility of the lesions, with dandruff shedding over clothing and centrofacial lesions on full display.
The histological abnormalities are practically identical to those in psoriasis and, as in psoriasis, accelerated inflammation and epidermal regeneration are observed. The presence of a large quantity of Malassezia furfur is noted around the lesions; it is not known whether this is the consequence of epidermal anomalies or if Malassezia furfur can play directly a pathogenic role, since it seems able to act as a superantigen. The therapeutic efficacy of imidazoles in seborrheic dermatitis is not a definitive argument since, besides destroying the Malassezia furfur, they have a direct anti-proliferative effect on the epidermis as well.
Seborrheic dermatitis is improved by the sun and is clearly stimulated by stress.
It develops through attack followed by remission, both of varying length, and many patients confine themselves to treating the attacks. In some cases, the attacks are subintrant and have an important impact on the subject’s quality of life. This is particularly the case with HIV infection.

Photo 103. Treatment is based on:

  • explanation of the disease to the patients. It needs to be underlined that this is an excessive skin reaction of genetic origin, and that treatment must therefore be continued indefinitely, much like some everyday personal hygiene application.
  • the use of imidazoles. Topical ketoconazole (Ketoderm®) is very effective but sometimes an irritant. Many patients can only use it two or three times a week. Instead, preference should be given to ciclopiroxolamine (Mycoster®/Ciclopirox® cream) to be used continuously every evening after washing and before bedtime.
  • some lithium salts are effective administered topically (Lithioderm?).
  • vitamin D derivatives are generally too irritating, with the probable exception of calcitriol (Silkis®)
  • tacrolimus (Protopic®) is highly efficacious in very resistant seborrheic dermatitis but this indication falls outside of the marketing authorization.
  • UVB is effective but its use is constricting. It causes an aggression largely incompatible with treatment over a very long period of time.
  • 13-cis-retinoic acid (Roaccutane®) is a remarkably effective treatment for resistant seborrheic dermatitis. It is active at very weak doses: 5 mg three times a week. At these doses, the side effects are very rare and wearing contact lenses is possible. However, biomonitoring every four months and, of course, contraception remains indispensable in fertile women.

In the case of seborrheic dermatitis combined with psoriasis, it is possible to combine small doses of 13-cis-retinoic acid to take care of the seborrheic dermatitis and acitretin to take care of the psoriasis. Side effects and clinical/biological monitoring are the same.
Acitretin is ineffective in seborrheic dermatitis and topical corticotherapy contraindicated. However, one week of daily use of a strength 3 topical steroid is often necessary before using Tacrolimus in order to avoid irritation.

An attack on the scalp is usually kept well under control by anti-dandruff shampoos, a foaming solution of ketoconazole (Ketoderm®), selenium sulphide (Selsun®), calcipotriol in lotion form (Daivonex® scalp solution) or topical corticosteroids in lotion form, which have practically no adverse effects on the scalp.

5.2. Palmoplantar pustulosis

Palmoplantar pustulosis is undoubtedly an autonomous disease. It illustrates a therapeutic plight often encountered in dermatology: the inflammatory response to be treated is highly localized but extremely vehement and, in order to be kept under control, requires the use of high-powered therapies that are not without their side effects. It is always difficult to chalk out a reasonable dividing line between impact on the quality of life that is severe but associated with highly localized lesions and the use of powerful drugs that may eventually have repercussions on the function of the liver or kidneys.
The sweat glands, particularly plentiful around the palms and soles, have often been suspected of playing a part in this ailment. Everything takes place as if the inflammatory response was structured around the substances secreted by the sweat glands. It is interesting to note that the case-control studies show that virtually all patients (90%) suffering from palmoplantar pustulosis are or have been heavy smokers. However, we cannot guarantee the patients that their condition will improve if they stop smoking.

  • The first line of treatment is based on topical corticosteroids, possibly combined with topical retinoids.
  • Phototherapy or PUVA therapy (combining generally and topically administered psoralens) is effective, but relapses occur usually and very quickly as soon as treatment stops.
  • Retinoids may be effective in reducing the number of pustules and improving the quality of life, but only exceptionally do they achieve complete clearance of the lesions.
  • Methotrexate® may be effective.
  • Cyclosporine® is often remarkably effective at very small doses (1.5 mg/kg/j). The problem is to know to what extent it is reasonable to give an immunosuppressant over a long period of time to patients who have been exposed for years to a powerful carcinogen tobacco.

5.3. Hallopeau’s acrodermatitis continua

[|Should this continue to cause destruction of the nail, and even the digit, systemic therapy is frequently indicated, including the traditional agents and biologic agents.|auteur215]

This pustulosis, still far more topicalized than the palmoplantar variety, in that it usually affects only a single finger albeit just as violently, poses the same therapeutic problems (photo 104). The highly topicalized nature of the lesions makes one even more hesitant to resort to general treatments, but topical treatments are really very ineffective indeed. Some practitioners claim good results with Protopic? under occlusive.

Photo 104.

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