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Editorial: Outlook in psoriasis.

Psoriasis is such an extremely variable disease in its manifestations and in its effect on patients that it is unwise to generalize about the outlook. The course varies from a single attack, never to be repeated, to progressive skin and joint lesions leading to increasing invalidism or rarely death. The large majority ofpatients fall somewhere between these two extremes, some suffering only trivial lesions, others having sufficient eruption to embarrass them when on the beach or at the hairdresser, and some combining these features with an arthropathy of varying severity. To the embarrassmentwhich depends very much on the attitude of the public (often deplorable) and of their spouses (usually understanding)is added a variable amount of itching; but that seems to depend more on the emotional state than on the extent and severity ofthe eruption, though the eruptive phase is intrinsically itchy. The one aetiological factor universally agreed is heredity, but the mode of inheritance is debated. Twin studies' and clinical observations suggest that environmental factors are also concerned. Probably there are many latent psoriatics, and until these can be identified progress in understanding the mode of inheritance is likely to be slow. Advance is also impeded because there is no experimental model, psoriasis being confined to mankind. Most races are affected, but it is probably absent in pure South American Indians2, while Caucasians are particularly susceptible. Was this perhaps why the ancients called psoriasis the leprosy of the Greeks ? The high incidence and early onset observed among the Faroese3 is probably due to a combination of an unfavourable climate with hereditary factors concentrated in an isolated community. Emotional stress plays an important though ill-defined part, while haemolytic streptococcal infections provoke attacks of guttate psoriasis, the one form carrying a good prognosis. Physical trauma provokes lesions during the "active" phases of the disease (the isomorphic response or Koebner phenomenon), the nearest thing there is to an experimental model. Attempts to define the course of psoriasis have always had to contend with the great variability of the disease, making it impossible to find a really representative group of patients, for some never see a doctor. The dermatologist's view is biased towards the more severe end of the spectrum. A recent survey by Molin4 suggested that psoriasis runs a more severe and progressive course in men than in women, but he thought himself that the method of selection might have contributed to this result. No support was found for the commonly-held belief that psoriasis protects from other diseases, and in fact the psoriatics were ill oftener than their controls. If advances in treatment have done a little to improve the lot of the psoriatic they have also made psoriasis a more dangerous disease. Systemic or fluorinated topical steroids suppress the eruption, but initial enthusiasm has changed to caution in view of the vigorous rebound of symptoms, including the severe generalized pustular form5, that is apt to follow their withdrawal. Not only is the dose required as a rule too high to contemplate for long-term use, but it is not unusual for the steroid requirement to increase progressively until an impasse is reached. Antimitotic agents, usually methotrexate, given systemically and intermittently are the latest method of treatment. These drugs are not suitable for those who may beget or conceive children, owing to the risk ofgenetic damage, and the treatment may cause cirrhosis of the liver (particularly in alcoholics), and bone-marrow depression, and may interfere with the natural defences against infections and neoplasia. Its use is therefore limited to incapacitated patients, especially those with severe arthropathy or exfoliative dermatitis, and then only under conditions that allow for careful monitoring throughout. Azathioprine6 is perhaps safer than methotrexate but seems less effective. The time-honoured applications of tar or dithranol and exposure to ultraviolet light remain the basis of local treatment. Topical fluorinated steroids should be used, if at all, either to get a rapid initial response or to treat difficult areas such as the palms and soles. Tar and dithranol are too messy to be popular for home use (the non-staining alternatives are less effective), and hospital outpatient clinics providing a local treatment regimen have a definite place.7 The combination of application of 8-methoxypsoralen and exposure to "black light" (wavelength < 360 nm) has recently been described as a clean method8 for use at such a clinic. Some patients come to accept their spots philosophically and cease to treat them except with an emollient, while others never become reconciled. If this assessment of the outlook in psoriasis appears rather depressing, the gloom is not unrelieved. Much of the large body of available information and current work on psoriasis is of academic rather than therapeutic interest at present, but the stage is being set for a synthesis of knowledge that will illuminate the scene. One spark is the discovery of a humoral anti-psoriasis factor.9 If this substance could be isolated it might be used therapeutically.