What is psoriasis?

It is a chronic non infectious inflammatory skin disorder, whose main symptom is gray or silvery flaky patches on the skin which are red and inflamed underneath when scratched.

Different theories have been put forward to explain the aetiology of the disease, but the precise cause of the disease is still unkown.

The Virus theory
Scientist have put forward many claims to prove this theory. Among these are: detection of elementary bodies and inclusion bodies in the affected tissues and organs; the presence of specific antibodies; susceptibility of laboratory animals (guinea pigs, rabbits_, albino-mice) to experimental infection; the ability of the causative agent to grow on chick embryo ( chorion allantois culture, etc). Some authors base their assumption of the existence of a specific causative agent of psoriasis on the systemic character of the process» the frequent association of the dermatosis with foci of local infection, and the spécific features of the clinical course (growth of the foci from centre to periphery, resolution of the lesion from the centre, involvement of the bones and joints by the type of rheumatoid polyarthritis, affection of the scalp and nails, and, in some cases, the acute abrupt character of the eruptions with elevation of body temperature.

The Hereditary Theory

The hereditary theory is based on the fact that, cases with pso­riasis are recorded among members of the same family. The concept of 'family’ not only includes children and parents, but also close relatives. According to various authors, familial psoriasis is encountered in 40 per cent of cases and even more frequently. Close relatives of the father have the disease relatively more frequently than mothers relatives. It is presumed that if a child of healthy parents has psoriasis, the probabiïity of the next child contracting psoriasis is estimated at 17 per cent, whereas if only one of the parents has psoriasis, the risk of the disease in the children increases to 25 per cent (in the event that both parents suffer from the disease, it rises to 60-70 per cent).

The Allergic Theory

The allergictheory, is based on the commonly known development of psoriasis following chronic tonsillitis, influenza, sore throat, pneumonia, exacerbation of focal infection or against the background of a latent infectious focus. The effect of staphylococcal or streptococcal infection on the origin and course of psoriasis, so clearly seen in children and adolescents, is substantiated by the authors with information on the high titres of antistreptolysin O and antistreptokinase in patients with psoria­sis, positive skin tests to high dilutions of staphylo- and strepto-allergens and the successful use of streptoantigen and staphylococcus toxoid in spécific hyposensitization of some patients. Authors supportîng the infectious-allergic theory of origin and course of psoriasis assume that it is a manifestation of allergie tissue réac­tion to the complex structure of viruses or the cells of staphylococci and streptococci or to the products of their vital activity. In view of this, notable importance is attributed to the rôle of chronic foci of infection, tonsillitis in particular.

Other theories put forward include:

The neurogenic theory

the metablic disorder theory

the endocrine disorders

Clinical picture.

In giving the general clinical characteristics of psoriasis, one should focus attention on the monomorphic nature of the papular psoriatic eruptions which in most patients is asymmet­rical and mainly localised on the extensor surfaces of limbs. At the same time, psoriasis, may occur on any area of the skin. The nails and locomotor apparatus are often involved. According to its course, this is a chronic récurrent dermatosis.

to be continued.....