6. DEVELOPMENT AND TRIGGER FACTORS

Overall, the way psoriasis develops is unpredictable, alternating between flares and more or less complete remissions. Everything takes place as if, under certain conditions - probably genetically determined for many patients, external events were capable of triggering outbreaks or facilitating remissions. These events vary from one sufferer to another, and it seems particularly important for each sufferer, with the help of his or her dermatologist and GP, to try to identify the factors responsible for flares or favourable to remissions. This self-observation will allow sufferers to manage their illness with increasing success and to greatly enhance the effectiveness of treatment.

A number of trigger factors have been identified:

• the skin traumas responsible for the phenomenon described by Köebner are the most familiar. Köebner’s phenomenon is chiefly observed in subjects undergoing a flare, but also in patients whose disorder started early in life and who present frequent relapses. Köebner’s phenomenon is observed in 38 to 76% of patients, according to studies. Psoriasis plaque appears one to two weeks after the triggering trauma (photos 44 and 45). The traumas concerned are extremely varied. Mechanical traumas spring firstly to mind (photo 46), of course, but any cutaneous inflammation connected with external agents or pathological events can bring upon a Köebner’s response. Therefore, one needs to look for evidence of contact eczema, of secondary skin infection, of lichen planus, of toxidermia or of scabies. Interestingly, psoriasis appears sometimes on a vitiligo patch, and there is no knowing of which direction Köebner’s phenomenon is working in: is the psoriasis promoting the vitiligo patch or vice versa? At experimental level, the majority of skin traumas can bring upon a Köebner’s response, but in order to observe this phenomenon, an epidermal and dermal wound usually has to be induced. It is noteworthy, however, that a psoriatic patch can be induced to appear after a suction or cantharidin blister is produced and the blister’s roof is removed.

Photo 44. Köbner’s phenomenon: the plaque appears in a traumatized area: on top of scratches (photo: C. Beylot).

Photo 45. Köbner’s phenomenon: the plaque appears in a traumatized area: on a tuberculin patch test (photo: C. Beylot).

• Infections, especially streptococcal sore throat, are a classic trigger for psoriasis and, particularly in children, for guttate psoriasis. The classic notion according to which eruptive guttate psoriasis disappears more easily is currently being questioned. On the contrary, it would seem that psoriasis that starts during infancy is often more progressive and more resistant to treatment.
• Endocrine factors can influence psoriasis, and more frequent attacks are observed at puberty and menopause. Psoriasis remains unmodified by pregnancy in 40% of female patients; in others, it may be improved or exacerbated, without being reproducible from one pregnancy to another in the same patient.
• The sun, and particularly sunshine coupled with sea baths have a favourable influence on psoriasis in 70% of patients.
  
  

  “ The effect of salt water alone is very small.

  Olle Larkö

  Olle Larkö
  The two have no effect in 20%. They can aggravate psoriasis in 10% of patients.
• Excess alcohol consumption is significantly linked with the occurrence of psoriasis. It is not known whether alcohol is directly to blame for eruptions or if such drinking is associated to a decrease in therapeutic compliance. It is certain that alcohol abuse lessens the efficacy of systemic treatments, probably by altering the metabolism of these drugs: psoralens, retinoids, methotrexate (whose toxicity it also increases) and probably cyclosporine. It is important to explain to patients that it is impossible to keep control of their psoriasis if they are incapable of keeping control of their alcohol consumption.
• The emotions have long been recognized as being able to trigger a psoriasis attack. A major emotion shortly before the first psoriasis attack is found in 46 to 80% of patients, according to studies. The psoriasis flare occurs between a fortnight and several months after the emotional trigger. The emotions are often connected with an acute or chronic attack in the areas in which any individual expresses himself (affective, professional, intellectual, artistic...). The patient is often someone who keeps his emotions under excessively tight rein or gives them little or no airing. The whole thing takes place, then, as if the patient was expressing some pent-up sensitivity through the skin, due to a particular genetic condition. It is very important to explore this avenue with the patient, because if this correlation is confirmed, any technique that allows him to give free rein to his emotions will make treatment more effective, making easier to keep the illness under control on the long run and allowing some alleviation of the psychological suffering caused by the illness.
• If tracing stress and emotions is an important part of a psoriasis flare beginnings, it is equally important not to forget medication. Independently of the toxidermias, all of which can trigger Köebner’s phenomenon, some drugs may aggravate or trigger a psoriasis attack. The most well known are the beta-blockers, lithium, an abrupt halt in systemic corticotherapy. Synthetic antimalarial agents may trigger severe attacks in some patients, but this complication is rare. Non-steroidal anti-inflammatory drugs (NSAID) may favour an inflammatory attack. Less frequently, potassium iodide, progesterone, the sulphonamides and clonidine have been held responsible for these attacks. Interestingly, some attacks of the disease have been clearly linked with taking angiotensin-converting enzyme inhibitors and calcium inhibitors, thus making the treatment of hypertension difficult in psoriatic patients.

Consensus and controversies forum