Psoriasis: a spectrum of expressions 
Review 
PSORIASIS: 
A SPECTRUM OF EXPRESSIONS 
P.C.M. van de Kerkhof 
SUMMARY 
Psoriasis is a frequently occurring skin condition caused by hereditary factors and triggered by environmental 
factors. Psoriasis has a heterogeneous expression pattern. Psoriasis may occur as chronic plaque psoriasis, 
erythrodermic psoriasis, psoriasis inversa and psoriasis guttata. In many patients the nails are involved as well 
and in one out of ten patients arthropathy complicates the picture. Before considering a treatment, non-
hereditary factors should be investigated and the patient should be informed about the factors, which may 
aggravate psoriasis. It is of importance that the patient is ascertained that psoriasis is not contagious and that 
the patients are informed about the risk of psoriasis in next generations. A treatment is selected based on 
the clinical expression of psoriasis, the acceptability of psoriasis for both the patient and his/her environment 
and the social circumstances of the patient. 
KEYWORDS 
epidemiology, epidermis, genetics, inflammation, proliferation, psoriasis, skin 
INTRODUCTION 
Psoriasis is a complex spectrum of expressions (1). 
Genetic factors as well as environmental factors 
determine the fate of psoriasis. In 1997 the possibilities 
for adequate treatment have been improved. 
acta dermatovenerologica A.P.A. Vol 7, 98, No 2 
EPIDEMIOLOGY 
Psoriasis occurs in 2% of the world population 
(2,3). However the occurrence of psoriasis is not 
distributed at ran dom over the world ( 4,5). Psoriasis 
is relatively seldom in American Indians and in the 
57 
Psoriasis: a spectrum of expressions 
Table l. Risk to get psoriasis (4) 
Family members Risk 
involved with psoriasis (%) 
One parent, no brother or sister 10 
No parent, one brother or sister 7 
One parent, one brother or sister 16 
No parent, two brothers or sisters 16 
Both parents 50 
Second grade fami ly 4 
Third grade family 1-2 
native population in the Far East. The low prevalence 
of psoriasis in black Americans is in line with the 
low prevalence of psoriasis in the black population 
of Western Africa as opposed to the frequency of 
psoriasis in the East of Africa. In Java, the frequency 
of psoriasis in Europeans was 30 times increased 
compared to the native population of Java. According 
to a study, carried out in the USA, 36% of the 
psoriatic patients stated that one or more family 
members were also affected by psoriasis (6). The 
male/female ratio is approximately l. 
The genetics of psoriasis is not determined by a 
single gene. Psoriasis is a polygenic inherited disease. 
Table 1 summarizes an estimation of the risks of 
reoccurrences of psoriasis in families in which at 
least one person is suffering from the disease. 
The age of onset of psoriasis varies considerably. 
Before the 25th year of age psoriasis had been 
expressed in the majority of patients (7,8). Psoriasis 
may occur already in children but may also occur 
for the first tirne at an advanced age. Environmental 
factors play an important role in the initiation of 
psoriatic skin manifestations in a genetically predis-
posed patient. 
Table 2. Triggering factors 
Triggering factors 
S)'.'.~temic; ~ 
. lnfections • Skin disorders . Stress • Trauma 
• Hypocalcemia 
acta demzatovenerologica A.P.A. Vol 7, 98, No 2 
Fig. l. Chronic plaque psoriasis 
Systemic factors may induce the expression of 
psoriasis after some days and weeks. Focal infections 
(tonsillitis, sinusitis, periapical granuloma, and cho-
lecystitis) may induce psoriasis guttata, or may change 
the picture from chronic plaque psoriasis into unstable 
psoriasis. Bacterial superantigens may induce an 
immune response, responsible for the inflammatory 
changes at this stage of the disease (Table 2). 
The relevance of psychological stress with respect 
to psoriasis has been debated. 
Some authors are of the opinion that psychological 
stress is virtually unimportant in the initiation of 
psoriasis (1), but other authors state that psychological 
stress is a triggering factor in psoriasis in 40% of 
the patients (1). The relationship between disease-
activity and psychological stress is difficult to assess. 
It is the opinion of the author that psychological 
stress is of major importance in the course of 
psoriasis. 
Fig. 2. Histological appearance of plaque psoriasis with 
prolongated rete ridges, parakeratoses and inflammatory 
in filtrate 
59 
Psoriasis: a spectntm of expressions 
Table 3. Local factors which may induce psoriasis 
SKIN DISORDERS 
Bites of insects 
Burns 
Dermatitis 
Drug reactions 
Excoriations 
Photosensitivity 
Herpes zoster 
lncisions 
Lichen planus 
Lymphangitis 
Miliaria 
Vitiligo 
Pityriasis rosea 
TREATMENTS 
Electrodesiccation 
Liquid nitrogen 
Pressure(belt) 
Primary irritants 
Radiation (UVR, X-ray) 
Scarification 
Skin tests (scratch, injection) 
Vaccination 
Various medications may induce psoriasis. Use of 
lithium carbonate, cardioselective, and non-cardio-
selective betablocking agents, antimalarial drugs, 
inhibitors of angiotensine converting-enzymes and 
non-steroid anti-inflammatory drugs. Also local factors 
aggravate psoriasis. Following injury of the skin 
psoriasis may occur within a few weeks. Various 
skin disorders induce psoriasis at the site of occurrence. 
Table 3 provides an overview of these external-
triggering factors. 
The induction of psoriasis following a local triggering 
factor has been described in 1883 for the first tirne 
by Heinrich von Koebner. The so-called "Koebner 
phenomena" occur in 25 % of patients with psoriasis. 
So far the genetics of psoriasis has not been 
resolved. Associations with HLA B13, B17, B27, 
B37, Cw6, and DR7 as well as the association with 
the apolipoprotein E-gene, the alpha-1 antitrypsine 
inhibitor g_ene and the gene of the interleukin-1 
receptor antagonist suggest a polygenic inheritance 
(9). On the other hand, various authors suggest a 
monogenic inheritance. Traupe and co-workers propo-
sed the concept of one major gene and genomic 
60 
imprinting, suggesting the relevance of some modifying 
genes (10). Recently a predisposing gene has been 
identified on chromosome 17 (11 ). 
Inflammation, increased epidermal proliferation, 
and abnormal keratinization are the hallmarks of 
the psoriatic plaque. Inflammation in the psoriatic 
lesion is characterized by accumulation of polym-
orphonuclear granulocytes and mononuclear cells in 
dermis and epidermis. A wide spectrum of mediators 
of inflamrnation has been reported to occur in 
psoriatic scales, varying from arachidonic acid meta-
bolites, interleukins, and platelet activating factors 
and complement factors. The pathogenetic relevance 
of these factors, so far, remains to be elucidated as 
we are not informed whether these factors are 
primarily or secondarily involved in the pathogenesis 
of psoriasis. 
A T-cell response and the accumulation of poly-
morphonuclear granulocytes probably play a major 
role in the pathogenesis of psoriasis (12,13). The 
dermis in the psoriatic plaque is abnormal in many 
respects. The endothelium is activated (14) and the 
stroma contains fibroblasts with an increased proteo-
glycan synthesis (15). The dermis of the psoriatic 
plaque is characterized by changes of the extracellular 
matrix with increased expression of the molecule 
tenascin (16). The epidermis of the psoriatic lesion 
is hyperproliferative with increased recruitment of 
cycling epidermal cells from the resting G
0 
com-
partment (17). The celi cycle of the epidermis in 
psoriasis is normal. A premature process of keratini-
zation with absence of stratum granulosum and a 
stratum comeum with rernnants of cell nuclei characte-
ERYTHRODERM IC 
PSORIASIS 
PUSTULAR 
PSORIASIS 
GUTTATE 
PSORIASIS 
Fig. 3. Spectrum of manifestations 
CHRONIC PLAQUE 
PSORIASIS 
acta dermatovenerologica A.P.A. Vol 7, 98, No 2 
Psoriasis: a spectrum of expressžons 
rizes the psoriatic lesion. 
Inflammation, epidermal proliferation, and abnormal 
keratinization are expressed at the macro leve! as 
erythema, induration, and scaling. 
PATHOLOGY AND CLASSIFICATION 
The symptomless skin of a psoriatic patient has a 
normal histological appearance. The clinically involved 
skin (Fig. 2) shows deviations at various levels. 
The expression of each of these features can be 
different comparing individual patients. If the 
inflammatory changes are dominating, macropustules 
filled with polymorphonuclear granulocytes can be 
farmed within the epidermis, The clinical picture in 
such a situation is psoriasis pustulosa. 
The extent of the body surface involved with 
psoriasis may vary from patient to patient. In some 
patients, psoriasis is restricted to some sharply dema-
rcated erythematosquamous plaques. This picture is 
designated as chronic plaque psoriasis. 
In other patients small erythematosquamous papules 
are distributed over the body surface. This picture 
is designated as psoriasis guttata. In patients with 
psoriasis guttata it is of importance to search far 
systemic triggering factors. In erythrodermic psoriasis 
the skin as a whole is involved. 
In fact faur prototypes identify the extremes of 
the psoriasis spectrum: 
(i) Chronic plaque psoriasis 
(ii) Psoriasis guttata 
(iii) Erythrodermic psoriasis 
(iv) Psoriasis pustulosa 
CLINICAL MANIFESTATIONS AND 
THEIR PROGNOSES 
Every patient has his own psoriasis with unique 
characteristics with respect to presentation and 
treatment response. The individual position of a 
patient with psoriasis is between the extremes of a 
three dimensional spectrum which can be constructed 
between the above mentioned prototypes (Fig. 3). 
(i) Chronic plaque psoriasis 
This manifestation is the most frequent one in 
adults. It occurs in 90% of the patients. Predilection 
areas are the extensor surfaces of the elbows (Fig. 
acta dennatovenerologica A.P.A. Vol 7, 98, No 2 
1 ), the knees, the sacrum, and the scalp. Lesions 
may occur on ali sites. The face is involved relatively 
seldom. The demarcation of the chronic plaque 
lesions is remarkably sharp. 
If psoriasis is triggered, and if new lesions occur, 
the patient may experience itch. Instable psoriasis is 
characterized by multiple papules and papulo-pustules 
around the psoriatic plaques. 
Chronic plaque psoriasis may occur at "difficult" 
localizations. These include the regio genitalis, including 
the mucous surfaces of the genitalia, the palms and 
soles and the flexures. Often a bacterial overgrowth 
ar a mycosis is a complicating factor, which triggers 
flexural psoriasis. In case of psoriasis of the scalp a 
loss of hair may occur. The course of chronic 
plaque psoriasis is chronic over years. In 10% of 
the patients remission periods of 5 years ar longer 
may occur (18). 
(ii) Psoriasis guttata 
Guttate psoriasis is characterized by multiple itchy 
erythematosquamous papules, distributed over the 
body (Fig. 4). Guttate psoriasis occurs predominantly 
in children. According to literature between 44-95% 
of the psoriatic children have this manifestation of 
psoriasis. Also at adult age, this variant may be 
seen in combination with other manifestations of 
psoriasis. As a rule systemic triggering factors are 
responsible far the occurrence of guttate psoriasis. 
Following elimination of systemic eliciting factors 
skin manifestations resolve spontaneously in a few 
weeks tirne. 
(iii) Erythrodermic psoriasis 
In erythrodermic psonas1s the skin as a whole is 
involved with erythema and scaling. In case of 
erythroderma, systemic complications may occur. The 
erythrodermic patient is poikylotherm with hypo-
and hyperthermia, protein loss, abnormal water-salt 
equilibrium, kidney insufficiency and cardiac 
insufficiency. Erythrodermic psoriasis may occur early 
ar late in the course of chronic plaque psoriasis. 
The course of erythrodermic psoriasis is variable. 
Goeckerman and O'Leary described the natura! course 
in 10 patients suffering from erythrodermic psoriasis. 
In 5 patients chronic plaque psoriasis developed, in 
2 patients erythroderma relapsed and in 3 other 
patients remissions occurred far 9 years. Eliciting 
factors are of major importance in the induction of 
erythrodermic psoriasis. In this respect it is of 
importance that antipsoriatic treatments with an 
61 
Fig. 4. Psoriasis guttata 
Fig. 5. Generalized pustular psoriasis 
62 
Psoriasis: a spectrum of expressions 
Fig. 6. Pustulosis palmoplantaris 
Fig. 7. Nail psoriasis. Subungual hyperkeratoses and 
distal onycholysis 
acta dermatovenerologica A.P.A. Vol 7, 98, No 2 
Psoriasis: a spectrum of expressions 
irritant potential such as photo( chemo )therapy and 
dithranol, may induce erythroderma. Discontinuation 
of systemic and topical corticosteroids may also 
induce erythrodermic psoriasis. 
(iv) Psoriasis pustulosa 
Psoriasis pustulosa may occur as generalized pustular 
psoriasis or localized pustular psoriasis. The pustules 
are sterile. Generalized pustular psoriasis is a relatively 
seldom condition characterized by episodes of erythema 
and pustule farmation (Fig. 5,6) with fever and 
feeling of illness. This phase may • occur far a few 
days and is fallowed by a phase of scaling. 
In an investigation of 104 patients in Great Britain, 
62 patients proved to have either chronic plaque 
psoriasis or psoriasis guttata befare the occurrence 
of pustular psoriasis (19). Triggering factors which 
may induce generalized pustular psoriasis are preg-
nancy, corticosteroid treatment, hypocalcemia, irritation 
( dithranol, phototherapy) and facal infections. The 
localized manifestations of psoriasis pustulosa can 
be divided into three subgroups. 
PSORIASIS ARTHROPATHICA 
In 5 - 10% of patients with psoriatic manifestations 
arthropathy may occur. Far a detailed review on 
psoriasis arthropathica the reader is referred to the 
literature (1). 
NAIL PSORIASIS 
Psoriasis of the nails is the result of changes in 
the nail matrix and nail bed. The nail matrix is the 
origin of the nail plate. If the psoriatic process 
affects the nail matrix, sharply punched out pits 
occur in the nail plate (Fig. 7). The extrusion of 
protein rich fluid under the nail plate causes brownish 
discoloration (oil spot phenomenon), and farmation 
of hyperkeratoses under the nail plate together with 
distal onycholysis of the nail plate from the nail 
bed. Fig. 7 demonstrates these features of subungual 
hyperkeratosis at distal onycholyses. The occurrence 
of nail-changes in patients with psoriasis varies between 
10 - 55%. 
DIFFERENTIAL DIAGNOSIS 
Chronic plaque psoriasis may be difficult to 
differentiate from seborrhoeic dermatitis. Involvement 
of the scalp and flexures may be rather similar in 
both conditions. A yellowish scaling is in favour of 
seborrhoeic dermatitis whereas the occurrence of 
psoriatic plaques elsewhere on the body is in favour 
of psoriasis. Psoriatic plaques with an elevated scaling 
border are suggestive of epidermomycoses. If the 
erythematosquamous plaque is not sharply demarcated 
parapsoriasis or lymphoma of the skin should be 
considered. Lues II should be considered in case of 
dissemination of erythematosquamous plaques on 
the trunk and involvement of palms and soles. 
Acknowledgements 
The authors wish to acknowledge Ms Sandra 
Pastoor far excellent secretarial support. 
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AUTHOR'S ADDRESS 
64 
Peter C. M. van der Kerkof MD, Professor and chairman, Department of Dermatology, 
University Hospital Nijmegen, PO BOX 9101, 6500 HB Nijmegen, Holland 
acta dennatovenerologica A.P.A. Vol 7, 98, No 2