A Short Glimpse of Psoriasis

 Psoriasis is a chronic and non infectious skin diseases. Psoriasis is affecting 2.5% of world population. It is characterized by well defined slightly raised, dry erythematous macule with silvery scale and typical extensor distribution and scalp. Course of disease is mainly goes through two phases i.e intermission and remissions. Attacks are more common in winter than in summer.

Psoriasis has been linked to HLA CW₆ and to a lesser extent to HLA-DR₇. Over 50% of patients with psoriasis report a positive family history.

Psoriasis can start at any age but exhibits two epidemiological patterns:-

₁₎ Onset in the teenage and early adolescence in these cases family history is positive  with very likely prevalence of HLA CW_{6 .}

₂₎Onset in 50s or 60s . Family history is less common and HLA CW₆ less prominent

According to many studies it is found out that the psoriatic plaques caused due to keratinocytes hyper proliferation with a glossy increased mitotic index and an abnormal pattern of differentiation involving the retention of the nuclei in the stratum corneum.  The transit time i.e., the time it takes for keratinocytes in the basal layer to leave the epidermis is shortened in psoriasis from perhaps 28 to 5 days which ultimately cause prosiatic plaques.

Precipitating factors include:-

Various factors are of importance in provoking new episode of psoriasis or in exacerbating pre-existing disease.

1)   Trauma

Psoriasis at the site of an injury is well known. Lesion appears in areas of skin damage such as scratches or surgical wounds (koebner’s phenomenon)

2)   Infection

B hemolytic streptococcal throat infection often precede guttate psoriasis

3)   Emotions

Anxiety precipitates some exacerbation

4)   Sunlight

            Rarely UV rays may worse psoriasis

5)   Alcohol and smoking

Alcoholism and smoking are not major factors that develops psoriasis but they may trigger flares

Common areas  where psoriatic lesion can be seen:-

 -  Scalp

-   Back of elbows

-  Front of knees and legs

-  Lower part of back and trunk

Uncommon areas:-

-  Palms and soles of feet

-   Nails

-  Genitals

Types of psoriasis:-

1)      Plaque psoriasis (psoriasis vulgaris)

2)      Flexural psoriasis (inverse psoriasis)

3)      Eruptive psoriasis (guttate psoriasis)

4)      Scalp psoriasis

5)      Nail psoriasis

6)      Psoriatic arthritis

Clinical features of psoriasis are:-

Psoriasis exhibits is a dry, well defined macule, papules and plaques of erythema with layer of silvery scales.

1)    coin shaped lesions, by confluence big plaques can be formed.

2)    candle-grease sign positive:-When a psoriatic lesion is scratched with the point of a dissecting forceps, a candle-grease like scale can be repeatedly produced even from the non scaling lesion..

3)    Auspitz sign positive:- The complete removal of a scale produces pin point bleeding.

4)    The lesions are slightly raised above the surface of the skin but there is no induration.

5)    Sometimes skin lesions of psoriasis can be itchy but not always.

6)    koebner’s phenomenon:- Psoriatic lesions may develop along the scratch lines in the active phase.

SEVERITY

Psoriasis is usually graded as mild (affecting less than 3% of the body), moderate (affecting 3-10% of the body) or severe. Several scales exist for measuring the severity of psoriasis. The degree of severity generally based on the following factors-

1)    The proportion of body surface area affected

2)    Disease activity (degree of plaque redness, thickening and scaling)

3)    Response to previous therapies

4)    Impact of the disease on the person

DIAGNOSIS

It is based upon:

Family history of psoriasis,typical distribution of the lesion,well defined, non indurated,dry, erythematous areas with silvery layer upon layer scaling, candle-grease sign , koebner’s phenomenon and pin point bleeding upon removal of the scale( auspitz sign ), Grattage sign- accentuation of scaling on scrapping the lesion, little or no itching, history of previous attacks and season variation of the disease and associated nail involvement and joint involvement.