Psoriasis is a genetically inherited, chronic, inflammatory skin condition that occurs in bouts. It affects around 1 % – 2 % of the population. A distinction is made between different forms of psoriasis. The most common form is psoriasis vulgaris, characterised by stubborn patches and plaques with thickening, redness and scaling of the skin, and occurring especially on the elbows, knees, scalp, the region of the coccyx, and the hands and feet. Other forms are accompanied by pustules (pus-filled blisters) and appear only on the palms of the hands and the soles of the feet. In rare cases, outbreaks of pustules can occur over the whole body, accompanied by fever, or redness and scaling of the whole body (psoriatic erythrodermia). Some patients also suffer changes to the nails. In the case of 5 to 8 % of patients, the joints of the limbs are additionally affected, while others only have inflammation of the joints without any visible symptoms on the skin.

The psoriatic skin changes can persist for months, or sometimes even years, in one localisation, or they can appear in a sudden attack and then disappear again after a few weeks. This spontaneous healing tendency can be found particularly with exanthematous psoriasis, which is characterised by the sudden appearance of small, scaly plaques over the whole body. In some patients, the psoriasis plaques are accompanied by itching, especially on the head and in the anal and genital area. Severe attacks of pustules over the whole body may be accompanied by a general feeling of illness, shivering attacks and fever.
The psoriasis bouts are triggered by various factors. These include chronic irritation through rubbing or scratching. Another trigger can be infections, especially with streptococci bacteria, for example streptococcal angina (“tonsilitis”). Typical for this form is the appearance of psoriasis plaques in small patches, with a relatively spontaneous healing tendency. Other provocation factors are stress, alcohol and cigarettes. Nicotine in particular sets off pustule attacks on the hands and feet. Psoriasis can also be triggered or aggravated by medication. This includes such things as betablockers, lithium, various anti-malaria drugs, interferon and systematic corticosteroides. Also severe overweight can contribute to stubborn psoriasis.

The therapy depends on the extent of the skin changes, the type of psoriasis, the localisation and the age of the patient.

Atypical feature of psoriasis vulgaris is the formation of thick plaques covered with scale, which can sometimes join up to form large areas. The plaques arise because the cells in the basal cell layer of the skin divide more quickly than normal. In healthy skin, a cell takes 28 days from leaving the basal cell layer to being rubbed off the skin as scale. In psoriasis plaques, this transit time is shortened to only 3 to 4 days. The result is the formation of thick, scaly patches. The goal of treatment is therefore to slow down this enormously accelerated rate of cell division in the basal cell layer. A number of substances applied either externally or internally can normalise this cell cycle. The precondition for the success of external treatment is, however, that the active ingredient is able to penetrate down to the skin layers responsible. A thick layer of scale, which frequently covers untreated patches of psoriasis, prevents good penetration and must therefore first be removed. To do this, mostly ointments with the addition of 3 – 10 % salicylic acid or 5 – 12 % urea are used. In particularly stubborn places like the scalp, where a stubbornly adhesive crust of scale sometimes forms around the hair shafts, these ointments can also be applied occlusively, i.e. under a film dressing or a bathing cap. When the crust has been removed, medications to slow down the cell division cycle are applied.


Psoriasisplaque | Foto: Eisfelder, Lizenz: Creative Commons by-sa 3.0 / Kurz

For inflamed forms of psoriasis which cause severe itching, creams and ointments containing cortisone are often initially given. These produce a rapid improvement. Unfortunately, however, discontinuation of the external cortisone preparations is frequently followed by a new, more severe attack. Treatment with cortisone should therefore be combined with other active ingredients, for example vitamin D analogues (derivatives of vitamin D, e.g. calcipotriol, calcitriol and tacalcitol). Also retinoids (derivatives of vitamin A acid) are effective. While derivatives of vitamin D are usually tolerated well and are likely to cause skin irritations only in the face or the intertriginous spaces, i.e. in skin folds such as the anal region or groin, retinoids often trigger initial irritations. They are therefore almost always combined with cortisone ointments. The substances/products named above differ positively from the “old” psoriasis treatments in that they neither cause discoloration to clothing nor have an unpleasant smell.

Just as effective as these new products is dithranol. All new psoriasis medication is still tested by comparison with dithranol. In terms of efficacy, dithranol is unexcelled. However, many patients find treatment with dithranol unacceptable as it produces dark brown disolorations of the skin and clothing. There is, however, now a product available in which the active ingredient is microencapsulated so that this discoloration is avoided. Dithranol preparations have also been in use for some time now in the form of “minute therapy”. This means that they are applied daily for a few minutes, with the time of application being gradually increased over several weeks, and the active ingredient then showered off again.
In the treatment of psoriasis, also tar ointments such as coal tar or tar extracts like liquor carbonis have proved successful. Tar ointments are especially good for forms of the illness with small plaques as they do not cause skin irritation and it therefore does not matter if they are also applied to the healthy skin.

Psoriasis is especially difficult to treat in the intertriginous zones, i.e. where skin rubs on skin, such as in the anal fold, the groin and genital region, or in the armpits. Because of increased sweating and rubbing in those areas, skin irritation frequently occurs. Also penetration into the skin, e.g. in the groin area, is up to 30 times higher than on the skin of the trunk. In these areas, mostly medications with cortisone, tar, or also tumenol (shale oil extract) can be used. Some patients also tolerate calcipotriol, calcitriol or tacalcitol, i.e. the vitamin D derivatives.
Another problematic area with psoriasis are the nails. A typical sign for when the nails are affected is pitting and so-called “oil spots”, i.e. yellowish spots under the nail that look as if a drop of oil had run under it. In severe cases, the nails become cracked and crumbly. The cause for all these changes is the increased rate of cell division in the nail matrix, i.e. the growth zone of the nails. Instead of a properly formed nail body, only inferior horn substance is produced.
As therapy, solutions with cortisone and vitamin D analogues are used, possibly also in combination or alternating in the morning and evening. Certain radiation techniques with radiation sources that penetrate the nail well, so-called bluepoint radiation, are sometimes also successful. However, radiation has to be performed daily over a period of weeks, which is very time-consuming.

psoriasis vulgaris

Psoriasis on the elbow | Foto: Userm1970, Lizenz: Creative Commons by-sa 3.0 / Kurz

For all manifestations of psoriasis, UV radiation is an optimum form of therapy. Nearly all psoriasis sufferers find that their condition improves in the summer months and on holiday in sunny regions. The effectiveness of some of the medications already mentioned, especially calcipotriol, calcitriol and tacalcitol, is increased in combination with light therapy (phototherapy). This can be performed in dermatological practices. On holiday, regions with high radiation intensity should be chosen for preference. For severe cases, there are also therapy centres in the appropriate geographical regions. These include dermatology clinics on the islands off the North Sea coast of Germany, at high altitudes such as Davos, or beside the Dead Sea. For UV therapy, UVB broad band radiation, UVB narrow band radiation around 311 nanometres, and selective UV phototherapy (SUP) are used. UVA radiation by itself is hardly effective, but can be used in combination with certain photosensitisers such as psoralen.

Psoralen is given in tablet form as a systematic treatment. A certain time after the tablets have been taken, to allow for resorption of the active ingredients from the stomach, UVA radiation therapy is performed. A problematic aspect with this form of therapy is an increase in light sensitivity which lasts the whole day, so that the patients are at higher risk of sunburn in summer. To protect the eyes, they are also required to wear special sunglasses offering good protection in the UVA range and with side visors throughout the whole time of the therapy. Other frequent side effects of systematic therapy of this kind are nausea and sickness, gastro-intestinal disturbances and, in some cases, liver problems. In the last few years, systematic PUVA therapy has been largely replaced by PUVA-balneology therapy. In this case, the patient must first take a bath containing psoralen solution, followed by treatment with UVA light. Special PUVA goggles need not be worn, and the increased light sensitivity of the skin, which makes the use of sunblockers essential in the sunny seasons, only lasts for a few hours.
Unfortunately, PUVA therapy has a number of long-term side effects. These include increased UV damage to the skin, with drying and with the formation of pigment spots (PUVA ephelides), which look like freckles and can occur in very large numbers. Accelerated deterioration to the connective tissue (actinic elastosis) with premature wrinkling has also been observed. Additionally, pre-cancerous keratoses, which must be seen as a pre-stage of squamous cell carcinoma, and squamous cell carcinoma itself are liable to develop. The risk of skin cancer increases with the cumulative dose of radiation exposure, i.e. the number of exposures and the strength of the radiation dose. Naturally, the risk also depends on the skin type. To reduce the radiation dose, PUVA treatment is also combined with the systematic application of retinoids, i.e. acitretin. This REPUVA treatment is today – apart from therapy with methotrexate and cyclosporin A – the most efficacious form of therapy, but should only be used for the most severe psoriasis cases. Treatment with systematic retinoids, i.e. acitretin, is especially problematic for women, as the substance is teratogenic (i.e. it can harm the foetus) and therefore it must be made absolutely certain that the woman is not pregnant. Also patients with liver or kidney problems as well as disturbances of the fat metabolism should only be treated with REPUVA in exceptional cases.

For severe psoriasis, fumaric acid and its derivatives can also be given internally. Fumaric acid is a metabolite ( a substance produced in the metabolism process) produced by the body. Therapy begins with a very low dose, which is then gradually increased. External application of fumaric acid derivatives (ointments, baths) should be avoided as absorption through the skin may undesirably increase the dose. The effects of the therapy begin to show themselves usually after 4 – 6 weeks. Side effects such as hot flushes, diarrhoea, gastrointestinal disturbances, increased need to go to the toilet, slight dizziness and tiredness may occur in the initial phase, before the positive effects of the therapy start to appear, but then they gradually disappear. By taking the medication in the evening, the flush symptoms can be “slept through”. Possible stomach problems can be lessened by drinking milk.

For the most severe forms of psoriasis, systematic therapy with cyclosporin A or methotrexate or combinations of methotrexate and cyclosporin A or cyclosporin A and acitretin is recommended.