ARTICLE
Auteur(s) :, Gang
Wang*, Chunying Li, Tianwen Gao, Yufeng Liu
Department of Dermatology, Xijing Hospital, Fourth Military
Medical University, 15 Changlexi Road, Xi’an 710032 China
accepté le 18 Janvier 2005
As we know, psoriasis characteristically often involves the trunk
and extensor surfaces of the extremities in a symmetrical fashion.
The commonly affected areas are the knees, elbows, sacral area, and
scalp. Yet in some cases, skin lesions are found in the groin,
genitals, umbilicus, and axillae, exactly the reverse areas of the
common distribution of the typical disease. For this reason, the
disease with such a lesion distribution is called inverse psoriasis
or flexural psoriasis [1, 2] Inverse psoriasis is a rare disease,
which has not been described in detail. During the period from
September 2002 to December 2003, a total number of 709 patients in
the dermatology clinic, Xijing hospital, Xi’an, China, were
diagnosed as suffering from psoriasis and 48 of them were diagnosed
with inverse psoriasis, counting for 6.8% of the total psoriasis
patients. In this retrospective study, we made a detailed analysis
of the clinical characteristics of inverse psoriasis.
Patients and methods
Diagnosis
Diagnosis of inverse psoriasis is made mainly on the basis of its
characteristic clinical features. With or without psoriatic lesions
at other parts, the skin lesions mainly involve parts with flexural
areas or mucous membranes like the vulva, groins, umbilicus, areas
below the breasts, axillae, antecubital fossae. Two senior
dermatologists were responsible for diagnosing all the patients.
Histological examinations were also performed in some of the cases.
Data collection and analysis
After the diagnosis was made, all of the psoriatic patients,
including those with inverse psoriasis, were requested to fill out
a Registration Form of Psoriasis. The form includes patient’s
general condition, gender, age, geographical data, dates of initial
occurrence and relapse, possible causing factors, affected areas,
association with seasons, family history, smoking and drinking
history, treatment history, etc. The clinical features of the
affected areas were recorded and kept in a file together with
photographs.
Treatment
Once a definite diagnosis was made, the patients were treated with
311 nm narrowband UVB (NB-UVB) therapy. The minimal erythema
dose (MED) of each patient was determined according to standard
protocols before the initial treatment. The initial dose was 70% of
the MED, around 350 mJ/cm2 for a normal Chinese person,
and the dose was increased at a rate of 15% for each additional
treatment. The therapy was conducted once every other day. Coal tar
shampoo (Zetar Lotion, Dermik) and topical corticosteroids were
supplemental therapies. For those patients who also have affected
areas beyond the typical lesions of inverse psoriasis, Tazarotene
gel or 20% urea cream was applied to those lesions which are not
typically seen in inverse psoriasis.
Results
Clinical data of the patients with inverse psoriasis are summarized
in table 1( Table 1 ). Among 48 cases of
patients affected with inverse psoriasis, 19 were male and 29 were
female, a ratio of 1:1.53. Their ages ranged from 5 to 67 years old
with the average being 39.2 years old. The average initial
occurrence occurred at 28.9 years old, mostly in springtime. There
were five new patients without any treatment history, and 43
patients who had been previously treated with more than one
therapy. The common treatments were topical corticosteroids, oral
Chinese herbal medicine, and oral retinoids. Thirty-three patients
took medications, such as bimolane, corticosteroids, or “Chinese
patent medicine” with unknown ingredients by informal
manufacturers.
Clinically, the skin lesions selectively involved flexural
parts, which, in a few cases, mainly involved the flexural parts
but were accompanied by sporadic skin lesions. To sum up, 46 cases
were psoriasis vulgaris, and 2 were pustular psoriasis. Skin
lesions showed sharply demarcated light or dark erythematous
plaques with varying infiltration and with little or no scales (
(figure 1) ). Of
the 32 patients who complained of itching (66.7%), four reported
smarting pain at affected areas. The most commonly affected areas
were the groin, followed by the axillae, genitals, umbilicus, anus
area, flexural areas below breasts, popliteal fossae, and
antecubital fossae. One of two pustular psoriasis cases was acute
generalized pustular psoriasis, accompanied by serious flexural
skin lesions with erosions and exudation. The other one had
erythematous plaques and pustules limited to flexural areas ( (figure 2) ). Seven
patients underwent a histopathological examination which showed
varying degrees of typical psoriatic features, like parakeratosis,
regular epidermal acanthosis, neutrophil microabcesses, capillary
ectasia in the papillary dermis, and superficial lymphocytic
infiltrate ( (figure
3) ).
Forty-five of the 48 patients completed four weeks or longer
treatment. Forty-one of them showed satisfying results (reduction
of PASI ≥ 80%), reaching an effective rate of 85.4%. Among the 32
patients who received treatment with narrow-band UVB, 26 persons
showed complete elimination of skin lesions, an effective rate of
81.25%. The rest of the patients showed improvement of no less than
80% and the lingering areas were anus area, vulva, and other areas
hard to reach by irradiation. Major side effects were skin
darkening and itching, which were soon improved upon discontinuing
the treatment or other appropriate therapies.
Table 1 Clinical data of the patients with inverse
psoriasis
|
No of patients
|
%
|
|
Sex
|
|
|
|
Male
|
19
|
39.6
|
|
Female
|
29
|
60.4
|
|
Seasons (initial occurrence/ recurrence)
|
|
|
|
Spring
|
17/28
|
35.4/58.3
|
|
Winter
|
15/20
|
31.3/41.7
|
|
Summer
|
7/6
|
14.6/12.5
|
|
Autumn
|
5/11
|
10.4/22.9
|
|
Unidentified
|
4/9
|
8.3/18.8
|
|
Family history of psoriasis
|
12
|
25
|
|
Regular smoker
|
10
|
20.8
|
|
With alcoholic preference
|
17
|
35.4
|
|
Distribution of skin lesions
|
|
|
|
Groin
|
46
|
95.8
|
|
Axillae
|
42
|
87.5
|
|
Genitals
|
38
|
79.2
|
|
Umbilicus
|
30
|
62.5
|
|
Anus area
|
26
|
54.2
|
|
Skin folds below breasts
|
16
|
33.3
|
|
Popliteal fossae
|
16
|
33.3
|
|
Antecubital fossae
|
9
|
18.8
|
Discussion
Inverse psoriasis, rare in clinical practice, is characterized by
erythematous plaques with or without scales in flexural areas, such
as the axillae, antecubital fossae, popliteal fossae, and inguinal
creases. It is also known as flexural psoriasis. Several clinical
investigations have shown that inverse psoriasis accounted for
about 3% of psoriasis vulgaris, and was relatively frequent among
children and the elderly [3-5]. According to our data, those
affected with inverse psoriasis accounted for 6.8% of the psoriatic
patients, higher than reported in the literature. It must be noted
that in some conditions, it is difficult to distinguish inverse
psoriasis from other diseases with similar clinical manifestations,
such as seborrhoeic dermatitis, eczema, and intertrigo. Family
history of psoriasis and typical skin lesions in other areas
contributed to the correct diagnosis. Summarizing from the clinical
analysis of the 48 cases in this article, inverse psoriasis is
characterized by the following features:
- (1) Most of the cases were psoriasis vulgaris, a few are
pustular psoriasis where affected areas were limited to the
flexural areas.
- (2) The major characteristic of the skin lesions was
sharply demarcated erythematous plaques with varying infiltration.
Most patients reported itching and a few had a smarting pain. There
was little or no scale compared with typical psoriatic
lesions.
- (3) The groin was the most commonly affected area,
followed by the axillae and external genitals. There was also a
report that the inverse psoriasis patients were usually subject to
skin lesions of the palms and soles simultaneously [6]. But our
study did not reach the same conclusion.
- (4) The percentage of female patients was slightly
higher than that of male. It is similar when compared to common
plaque psoriasis with regard to age, seasons of occurrence, family
history, and the response to NB-UVB therapy.
It is still unknown why inverse psoriasis selectively affects
the flexural areas. Possible explanations are maceration due to a
larger amount of perspiration, body fluid exudation, and associated
physical and chemical stimulations. In the case of an overweight
patient, similar skin lesions were also found in skin folds at the
sides of the waist, which supports the above speculations.
Inverse psoriasis can be difficult to treat because of the high
sensitivity of the intertriginous areas. Application of irritant
topical agents should be avoided [7, 8]. Tacrolimus and
pimecrolimus, the well-tolerated, non-atrophogenic, skin-selective
inflammatory cytokine inhibitors, have been shown to be effective
in the treatment of inverse psoriasis, when applied topically
[9-11]. Our combination therapy with NB-UVB achieved a satisfactory
effect. To effectively apply NB-UVB irradiation, appropriate
positioning of the patients is necessary so that most of the skin
lesions can be exposed to the radiation. According to a recent
report, the therapy of spot radiation with the 308 nm excimer laser
is encouraging in its treatment effects [12]. It can be expected
that the 308 nm excimer laser would be more effective for the
affected areas hard to reach with total body NB-UVB therapy.
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