PSORIASIS

Psoriasis is a chronic dermatosis characterized by well defined , erythematous , scaly plaque with silvery scales and an unpredictable course .
ETIOLOGY & PATHOGENESIS
The cause of this chronic dermatosis still remains an enigma . Theories about the pathogenesis run parallel to the fashionable concepts in cell biology – the current vogue being cytokines and adhesion molecules . Some biochemical abnormalities have been detected – these could either be the cause or may be the effect of the disease . There is often a genetic predisposition and the disease may sometimes be precipitated by an obvious trigger .
Genetics
Studies of family trees have suggested that psoriasis is inherited as an autosomal dominant trait with an incomplete penetrance ; but there is also evidence to suggest that it may have a polygenic inheritance . Psoriasis by itself is genetically heterogeneous .
A child with one affected parent has a 15 % chance of eventually developing the disease , but if both parents are affected this risk rise of 3 – fold . If non – psoriatic parents have a child with psoriasis , the risk of subsequent children developing psoriasis is 10 % . The disorder is concordant in 70 % of monozygotic twins but only in 20 % of dizygotic twins .
Genetic predisposition is further supported by studies on linkage to HLA . Early onset psoriasis shows an obvious hereditary element with linkage to HLA _ CW6 ( 20 times risk of developing   psoriasis ) . The association are much less with adult onset psoriasis .
TRIGGERS FACTORS or CAUSES
TRAUMA : In active psoriasis , lesion of psoriasis appear in skin damaged by scratches , surgery , injury etc . ( Koebners’s or isomorphic phenomenon ; iso means similar , morph means form ) .
INFECTION : Haemolytic streptococcal infection is known to precipitate attack of guttate proriasis . HIV infection often worsens psoriasis or triggers episodes of explosive psoriasis .
DRUGS : Anti – malarial , lithium , & beta blockers worsen psoriasis . Patient on corticosteroid therapy ( both systemic & topical ) may experience a “ rebound “ (exacerbation ) when the steroid are withdrawn . non steroid anti inflammatory drugs which are often used in patients with psoriasis because of concomitant may also aggravate the skin lesions .
OTHERS :Sunlight helps about 90 % of patient tseen by the frequent improvement of psoriasis during pregnancy with post – partum relapses . Cigarette smoking & alcohol may have an independent effect in precipitating psoriasis . Emotion upsets seem to cause some exacerbation too .
Epidermal cell Changes
Two changes are notable in psoriasis :
Increased epidermal proliferation : This is due to an excessive number of germinative cells entering the cell cycle as well as due to a decrease in cell cycle time
Altered epidermal cell maturation : The most visible manifestation of abnormal keratinisation is the presence of nuclei in the stratum corneum .
DERMAL CHANGES
Two important changes :
The dermal capillary loops in psoriasis are abnormally dilated and tortuous.
Fibroblast in psoriatic lesion proliferate more rapidly and produce more ground substance .
BIOCHEMICAL CHANGES
Cyclic nucleotides , arachidonic acid , polyamins , proteinases ,
IMMUNOLOGICAL CHANGES
T lymphocyte play a central role .
CLINICAL FEATURES
. Occures at any age
. Female tend to develop psoriasis earlier than man
. ratio of male : female is equal
. worse in winter
. A few patients , however , complain of summer aggravation
MORPHOLOGY
Well demarcated , erythematous , scaly indurated plaque . The colour is deep PINK to RED , the quality of this colour is sometimes lost in dark – skinned individual . The psoriatic plaque are often encircle by clear halo – the ring of WORONOFF .
The lesion pathogonomonically have silveary white scales , though the amount of scaling can be variable . In some cases the scsles are healed up , the so called RUPIOID scaling . Scaling is accentuated by grafting the lesion with a glass slide – this test is useful in diagnosing uncertain lesion ( Grattage test ) . A useful bed side test to confirm the diagnosis is the AUSPITZ sign .
This is performed by gradually scraping off the silvery white scales ( STEP - A ) . After the scsle have been removed , a glossy membrane appears ( STEP – B ) . On removal of the membrane , puncate bleeding points become apparent ( STEP – C ) .
The lesions of psoriasis are well defined , initial ly being discoid . When they merge , annular & gyrate lesion may be seen . The sharp demarcation of lesions is of special diagnostic significance on the scalp , flexures , & on the uncircumscised penis where other evidence of psoriasis , like characteristic scaling , may be absent .
The size & number of lesions can be variable ; when multiple lesion may be symmetrical .
SITES OF PREDILECTION
It can occur at any part of the body .
Common & early sites of involvement are the scalp & the pressure points ( knees , elbow ) & the lower back .
PATTERNS OF INVOLVEMENT
Plaque Psoriasis : This is the commonest type of psoriasis . The lesion variable from few millimetres to several centimeters , may be single or multiple . The site of prediction are the scalp , pressor point & lower back .
Guttate Psoriasis : This pattern of psoriasis is commonly seen in children & adolescents . The attack is often precipitated by streptoccal tonsillitis . The lesion appear as crops of tiny psoriasiform papule on the trunk . The lesion either clear or they may eventuate into plaque psoriasis .
Rupioid Psoriasis : these psoriatic plaques have massive healed – up scales – the lesions appear limpet –like & cone shaped .
MODIFICATION BY SITE
SCALP : The scaling may be massive especially on the occiput . Frequently the whole scalp is diffusely involved & there is on overflow beyond the scalp margin . sometimes the scaling is asbestose –like , being firmly adherent to scalp .This entity is called PITYRIASIS AMIANTACEA .
PENIS : In uncircumcised males , psoriatic plaques on the glans lack scales but the colour & well defined edge are characteristic .
FLEXURAL PSORIASIS : Psoriasis the groin , vulva , axillae , infra-mammary folds & gluteal cleft ( all flexure area ) is most frequently seen in elderly females . Scaling is understandably less in this moist areas , but the colour & demarcation are retained . Sometimes the depth of fold is fissured . Flexure psoriasis needs to be differentiated from intertrigo .
PSORIASIS OF HANDS AND FEET : Psoriasis of the palms & soles appears as bilaterally symmetrical erythematous plaques . It may sometimes closely resemble eczema , but can be distinguished by a sharp edge at the wrist & absence of vesicles .
NAILS :Nail involvement is frequent ( more the half the patients ) . The most frequent manifestation is pitting : small regularly placed pits as seen on the thimble . Other changes seen are ONYCHOLYSIS ( separation of nail plate from nail bed ) , subungual hyperkeratosis ( accumulation of keratinous material under the nails ) , thickening of the nail plate & discolouration of nail plate.
COMPLICATION
1 . ERYTHRODERMIC PSORIASIS : The psoriatic plaque lose their definition and the skin becomes universally & uniformly red ; there may be marked scaling .
2. PUSTULAR PSORIASIS : Psoriasis can be complicated by the appearance of sterile pustules . Pustulation may be trigged by the irritant effect of topical therapy or withdrawl of tropical or systemic corticosteroids . The postulation can occur in localized areas as seen in palmoplanter psoriasis or can be generalized . the latter variety , VON ZUMBUSCH’S pustular psoriasis is a rare & serious condition accompanied by constitutional symptoms .
3 . PSORIATIC ARTHROPATHY : Arthritis occurs in about 10 % of psoriasis patients .
INVESTIGATION
Histopathology :
. Parakeratosis (nuclei return in the horny layer )
. Regular acanthosis ( thicking of vible epidermis ) with thinning of epidermis over dermal papilla ( this is responsible for the Auspitz sign ) .
. Collection of polymorphs in the epidermis forming micro – abscesses .
. Dilatation & tortuosity of capillary loops in the dermal papilla ( cause of Auspitz sign ) .
. Lymphocytic infiltrate in the upper dermis .
DIAGNOSIS
Diagnosis is based on three main clinical criteria :
. Definition ( well defined ) of lesion .
. Colour ( deep red ) of lesion .
. Scaling ( silvery ) with positive grattage test & Auspitz sign .
. In case of doubt , a biopsy is helpful .
POINTS OF FOCUS : clinical feature of psoriasis
. OCCUR AT ANY AGE
. ERYYHEMATOUS , WELL DEFINED PLAQUE WITH CHARISTICALLY SILVERY SCALES ,ACCENTUATED BY GRATING THE LESION ; Auspitz sign positive .
. SCALP & PRESSURE POINTS frequently involved .
. PATTERN SEEN : plaque , guttate , rupioid lesion ; lesion may be modified by site .
. ASSOCIATIONS : Nail changes , arthritis .
. COMPLICATION :Erythroderma , pustular psoriasis.
COMPLICATION
PSORIASIS SHOULD BE DIFFERENTED FROM :
. Discoid eczema : lesion of discoid eczema are not as well defined as psoriasis . Lesion are exudative & are crusted ( of psoriasis where the lesion shows scaling ) & are very itchy ( psoriasis may or may not be itchy ) .
. Seborrhoeic eczema : Scalp involvement in seborrhoeic eczema is more diffuse , less lumpy & lesions do not spill over onto the forehead . Flexural lesions of seborrhoeic dermatitis are less well defined , when compared to psoriasis & are more exudative .
. Pityriasis rosea : The lesions of pityriasis rosea are oval & tend to run along the rib lines . Scaling is present at periphery of the lesion ( collarette ) & a large patch heralds the eruption ( herald patch ) .
. Secondary syphilis : The secondary eruption of syphilis is usually precided by history of primary chancre on the genitalia . The full picture is completed by the presence of mucosal lesions , lymphadenopathy , coppery scaly lesions on the palms & soles & condyloma lata at mucocutaneous junctions .
TREATMENT
The treatment of psoriasis should be individualized depending on the age & sex of the patient & the type , extent , duration of psoriasis .
GENERAL MEASURES
Reassurance & emotion support are invaluable . physical & mental rest may enhance the effect of the specific management of acute episodes . At present there is no permanent cure for psoriasis – all treatment are suppressive , only including remission . They do not prevent relapse , which are generally the rule . It is important to stress to the patient that the disease is not contagious & is benign . It is equally important to inform the patient about the natural course of the disease .
TYPE OF PSORIASIS                                    TREATMENT OF CHOICE                                       ALTERNATIVE TREATEMENT
1.Localised            short – contact         topical steroid
Stable plaque        dithranol TAR
2 . Extensive         UVB , PUVA              methotrexate ,
Stable plaque                                           cyclosporine ,
                                                                   Etretinate
3 . Widespread      UVB , PUVA             tar
Small plaque
4 . Guttate             antibiotic and           weak tar
                               Emollients while           preparation
                               Erupting ; PUVA            mild local
                                                                        Steroids .
5 . Facial               mild topical
                                   Steroids
6 . Flexur              mild to moderately
                                 Potent steroids +
                               Anti fungal
7 . Pustular            topical moderately        methotre-
Psoriasis of            potent or potent                   xate
Hands & feet            steroids                       ( small
                                                                          Doses )
8 . Acute eryth-       methotrexate +       acitretin ( if
-rodermic , unstable        topical                available )
Or generalized           bland application cyclosporinA
Pustular
PUVA
. Variation of PUVA : Some innovations of PUVA therapy are :
*PUVA solution : This make use of solar energy as source of UVA .
* Topical PUVA /PUVA solution : Graded UV exposer , 1 hour after application of topical psoralen .
* Bath PUVA : Another way to deliver the psoralen is by adding it to bath water .
Advantage :
. Reduce cost
. Major advantage of topical
PUVA & bath PUVA are :
*Lack of systemic effect ( especially nausea )
* Lower UVA dose
* No eye protection needed
Indication
         *Palmoplanar psoriasis
         * Extensive plaque psoriasis
         * Psoriatic erythroderma