Epidemiology and clinical features of pediatric psoriasis in tertiary referral psoriasis clinic


  • Conflict of interest: There is no financial support or conflict of interest.

Jai Il Youn, M.D., Ph.D., Department of Dermatology, Seoul National University College of Medicine, 28-Yongon-dong, Chongno-gu, 100-744 Seoul, Republic of Korea. Email: jaiil@snu.ac.kr


Few epidemiological studies of pediatric patients with moderate to severe psoriasis have been available despite there being no approved systemic therapy for these patients. The aim of the present study was to elucidate clinical features of pediatric psoriasis in a tertiary referral psoriasis clinic. We analyzed the clinical data of 358 patients under 18 years of age referred to our clinic from other private clinics and medical centers. Our data showed a male : female ratio of 1.06:1 and a peak age of onset of 10–11 years. Of the patients, 32.4% had a positive family history. The most prevalent phenotype was plaque type (67.3%) and the mean Psoriasis Area and Severity Index score was 17.2 ± 12.7. The most frequently affected body part was the trunk (69.5%), followed by the legs (65.3%). Exposure to sunlight and summer season improved psoriatic lesions, while stress and winter season aggravated the clinical course. Only 26.0% of patients received systemic therapy or phototherapy during the therapeutic course. Oral acitretin (11.2%) was most frequently used followed by ultraviolet B phototherapy (7.3%). The childhood group (<13 years) showed higher prevalence of guttate and generalized pustular phenotypes and more severe clinical course compared with the adolescent group (13–18 years). In conclusion, our patients showed distinctive features in clinical phenotypes, disease severity and affected body parts compared with previous reports. We also found that clinical application of systemic therapies were limited considering the severe disease state of our patients, demanding a need for more research on treatment of pediatric psoriasis.


Although pediatric psoriasis generally shows a mild clinical course, a certain group of patients present with severe disease which is poorly controlled by conventional treatments.1–7 Clinical studies for these patients have rarely been performed although they are required for the following reasons. First, it has been known that the quality of life of children with severe psoriasis is even worse than those with childhood diabetes and epilepsy.8,9 Second, pediatric psoriasis has also been reported to accompany significant comorbidities compared with the normal population like adult psoriasis. The prevalence of serious diseases including Crohn’s disease, diabetes mellitus and rheumatoid arthritis is significantly higher in juvenile patients with psoriasis.10 Finally, there is no systemic therapy for pediatric psoriasis currently approved by the US Food and Drug Administration. Clinical application of systemic treatments including oral medications and phototherapy is limited because they have possible cumulative adverse effects, teratogenicity and low acceptability in this age group.11–14 While a few epidemiological studies of different ethnic origins have reported clinical features of pediatric psoriasis, most patients in these studies showed mild disease courses.1–6 Because our hospital provides a two-step care system for psoriatic patients in this age group, our patients generally present with moderate to severe psoriasis. Herein, we report clinical features of pediatric psoriasis in a tertiary referral psoriasis clinic in Korea.



Between April 1985 and November 2010, 382 pediatric patients visited psoriasis clinic in Seoul National University Hospital, Seoul, Korea. At their first visit to the clinic, medical information was acquired. Of these, except for the records of 24 patients who refused to complete the patient questionnaire and submitted incomplete answers, data of 358 children and adolescents were analyzed (184 male and 174 female, mean age 13.7 ± 4.0 years, range 0–18 years). Pediatric patients comprised 8.2% of all patients visiting our clinic during the study period. In our hospital, we provide a two-step care system for psoriatic patients in this age group. Although the criterion has not been definitely established, patients with mild psoriatic lesions were generally treated in the pediatric dermatology unit and patients with moderate to severe degree were cared for in the psoriasis clinic. Patients resistant to the treatments of the pediatric dermatology unit were also referred to the psoriasis clinic. This study was approved by the Institutional Review Board of Seoul National University Hospital.

Study design

At the patients’ first visit, clinical records including a psoriasis chart and a patient questionnaire were acquired. On a psoriasis chart, dermatologists evaluated the patients’ clinical characteristics including age of onset, family history, Psoriasis Area and Severity Index (PASI) score, extent of involvement, disease activity, clinical phenotypes, nail involvement and all body parts affected by psoriasis at the time of the visit. The extent of involvement was defined according to the classification suggested by Molin15 at the beginning of the study: mild (<5% involvement of the whole body surface area); moderate (5–30% involvement of the whole body surface area); and severe (>30% involvement of the whole body surface area). Activity was defined according to the classification suggested by Haftek et al.16 at the beginning of the study: mild (stationary skin lesions for the last 1 month); moderate (peripherally spreading plaque lesions with occasional small papules); and severe (rapidly developing new lesions from the periphery of plaques or normal skin, or newly developing pustules). In most patients, clinical photos were taken and the extent and activity of skin lesions were reviewed by other dermatologists. Clinical phenotypes were classified a guttate, plaque, generalized pustular pustulosis (GPP), palmaris et plantaris (PPP) and erythroderma type. The guttate type was defined when the individual lesion predominant in a patient was less than 1 cm in diameter. The plaque type was further classified as nummular type (when the individual skin lesion predominant in a patient was 1–5 cm in diameter) and large plaque type (when the individual skin lesion predominant in a patient was >5 cm in diameter). Patients filled out the questionnaire before treatment. The contents of the questionnaire included the degree of pruritus on psoriatic skin lesions, external factors affecting disease course (i.e. sunlight, winter, summer and stress) and past treatment histories before visiting our clinic. The degree of pruritus was presented as follows: none; mild (felt sometimes); moderate (interrupting daily life); and severe (difficult to sleep). Patients’ responses about external factors were largely divided into four categories: improved; stationary; aggravated; and wax and wane. The total pediatric patients were divided into two age groups in comparing clinical characteristics based on a recent Korean journal of pediatrics: (i) children (aged 0–12 years); and (ii) adolescents (aged 13–18 years).17

Statistical analysis

Statistical analysis was mainly performed to compare between the childhood and adolescent group. Fischer’s exact test was used to analyze categorical variables. Categorical values were denoted as frequencies and percentages. Continuous data were described as mean and standard deviation. All significance tests were two-tailed. For all analyses, probability values of 5% or less were regarded as being statistically significant. Statistical analysis was performed using SPSS software for Windows (ver. 17.0.1).


The epidemiological data of our patients are shown in Table 1. The male to female ratio was 1.06:1 and the mean age of the childhood and adolescent groups was 8.8 ± 2.4 and 16.2 ± 1.5 years, respectively. The mean onset age of each group was 7.1 ± 3.0 and 12.4 ± 3.8 years, respectively (10.5 ± 4.3 for all patients). A total of 116 (32.4%) patients had a first-degree family history including parents and siblings. Thirty (8.4%) patients had been admitted more than once. Clinical data of phenotypes, disease severity, pruritus and nail involvement in childhood and adolescent groups are compared in Table 2. Overall, the plaque type (67.3%) including nummular and large plaque type was most frequently observed.

Table 1.   Demographic characteristics of total patients (n = 358)
 Sex (M/F)Mean age (years)Onset ageFamily history* (%)Admission history (%)
  1. *Family history included only first-degree relative including parents and siblings in the questionnaire. Patients were divided into childhood and adolescent group by the age criterion of 12 years according to a recent pediatrics publication from Korea.17

Children (0–12 years)
n = 129
 69/608.8 ± 2.47.1 ± 3.033 (25.6)13 (10.0)
Adolescents (13–18 years)
n = 229
115/11416.2 ± 1.512.4 ± 3.883 (36.2)17 (7.4)
Total35813.7 ± 4.010.5 ± 4.3116 (32.4)30 (8.4)
Table 2.   Clinical phenotypes, disease severity, pruritus and nail involvement of childhood and adolescent psoriasis
 Childhood (0–12)
n = 129 (%)
Adolescence (13–18)
n = 229 (%)
Fischer exact test (P-value)
  1. *Guttate type was defined when the individual lesion predominant in the patient was <1 cm in diameter. Plaque type was further classified as nummular type (when the individual skin lesion predominant in the patient was 1–5 cm in diameter) and large plaque type (when the individual skin lesion predominant in the patient was >5 cm in diameter). Activity criterion is based on16 (mild, stationary skin lesion for the last 1 month; moderate, peripherally spreading plaque lesions with only occasionally small papules; severe, rapidly developing new lesions from the periphery of plaques or normal skin, or newly developing pustules). GPP, generalized pustular pustulosis; PASI, Psoriasis Area and Severity Index; PPP, palmaris et plantaris.

Clinical phenotypes*
 Guttate35 (27.6) 31 (13.5)<0.01
 Nummular41 (31.8)117 (51.1)<0.01
 Large plaque26 (20.2) 57 (24.9)0.36
 GPP15 (11.6) 11 (4.8)0.04
 PPP 5 (3.9)  8 (3.5)0.99
 Erythroderma 2 (1.6)  2 (0.9)0.62
 Others 5 (3.9)  3 (1.3)0.14
PASI score
 0–5 7 (5.4) 25 (10.9)0.02
 5–1039 (30.2) 95 (41.5)
 10–2044 (34.1) 67 (29.3)
 20–3527 (20.9) 33 (14.4)
 >3512 (9.3)  9 (3.9)
Mean20.7 ± 15.0 15.6 ± 11.3 
Body surface extent
 <5%29 (22.5) 53 (23.1)0.38
 5–30%54 (41.9)110 (48.1)
 >30%46 (35.7) 66 (28.8)
Disease activity
 Mild23 (17.8) 54 (23.6)0.01
 Moderate47 (36.4)108 (47.2)
 Severe59 (45.7) 67 (29.3)
 None19 (14.7) 55 (24.0)<0.01
 Mild49 (38.0)122 (53.3)
 Moderate47 (36.4) 33 (14.4)
 Severe14 (10.9) 19 (8.3)
Nail involvement25/93 50/1700.79

Specifically, guttate, nummular and GPP types were significantly more common in childhood psoriasis compared with adolescent psoriasis (P < 0.05). The mean PASI score of total patients was 17.2 ± 12.7. PASI score and disease activity of the childhood group were statistically more severe than those of the adolescent group. Childhood patients complained of more severe pruritus compared with the adolescent group (P < 0.01). There was no statistical difference in nail involvement between the two groups (P = 0.79). Body parts affected by psoriasis are demonstrated in Table 3. The trunk (249 children, 69.5%) was the most frequently affected body part in our patients followed by the legs (234 children, 65.3%) and scalp (207 children, 57.8%). Facial involvement of psoriasis was 46.3% (166 children) of total patients. Among external factors known to influence clinical course of psoriasis, patients answered that sunlight exposure and summer season were helpful in improving disease state while winter season and stress aggravated disease course (Table 4). Approximately 38.8% of patients experienced overall improvement of psoriasis in summer while 50.0% of patients experienced aggravation during winter. Total treatment methods during a whole therapeutic course are demonstrated in Table 5. Topical steroids were used by 339 children (94.7%), vitamin D ointment by 223 children (62.3%) and tacrolimus ointment by 45 children (12.6%). Most steroids used in our clinic were of mild to moderate potency. Systemic treatments were administrated to 116 children (32.4%). Oral acitretin was the most common medication (40 children, 11.2%), followed by cyclosporin (15 children, 4.2%). Phototherapy was administrated to 41 patients (11.5%) and ultraviolet B therapy was the most frequently used method (26 children, 7.3%). No biologic therapy was used in our patients. In comparison with adult psoriatics (aged >18 years) visiting our clinic, clinical characteristics of pediatric psoriatics were not significantly different except the proportion of guttate, GPP and erythroderma types (8.4%, 0.8% and 2.8%, respectively, in adult psoriasis). However, the average number of treatment modalities administrated to individual patients in adult psoriatics (n = 2.9) were higher than those to pediatric psoriatic (n = 2.1) (P = 0.03).

Table 3.   Localization of psoriatic lesions in children and adolescents
 No. of patients (%)Percentage of cases
  1. Physicians at psoriasis clinic recorded all body parts affected by psoriasis at initial examination.

Body parts
 Scalp207 (18.3)57.8
 Face166 (14.7)46.3
 Trunk249 (22.1)69.5
 Arms170 (15.1)47.5
 Legs234 (20.7)65.3
 Palms and soles77 (6.8)21.5
 Other sites26 (2.3)7.3
Total1129 (100.0)315.4
Table 4.   Effects of various external factors affecting clinical course of psoriasis
 Sunlight (%)Winter (%)Summer (%)Stress (%)
 Improved139 (38.8)32 (8.9)139 (38.8)20 (5.6)
 Stationary90 (25.1)54 (15.1)74 (20.7)105 (29.3)
 Aggravated26 (7.3)179 (50.0)51 (14.2)145 (405)
 Wax and wane103 (28.8)93 (26.0)94 (26.3)88 (24.6)
Table 5.   Treatments administrated to pediatric patients
 No. of patientsPercentage of each method
n = 129 (%)n = 229 (%)n = 358 (%)
  1. Medical treatments applied since the first visit of our clinic were analyzed by retrospective chart reviews. Medications prescribed in other departments were not included in the data. *UV-B therapy included both broadband UV-B therapy and narrowband UV-B therapy. PUVA, psoralen and ultraviolet A therapy; UV, ultraviolet.

Topical treatment
 Steroids120 (93.0)219 (95.6)339 (94.7)44.6
 Vitamin D93 (72.1)130 (56.8)223 (62.2)29.3
 Tacrolimus12 (9.3)33 (14.4)45 (12.6)5.9
 Anthralin3 (2.3)10 (4.4)13 (1.7)1.7
 Others9 (7.0)15 (6.6)24 (6.7)3.2
Systemic treatment
 Acitretin10 (7.8)30 (13.1)40 (11.2)5.3
 Cyclosporin3 (2.3)12 (5.2)15 (4.2)2.0
 Methotrexate3 (2.3)4 (1.7)7 (2.0)0.9
 Oral steroid2 (1.6)11 (4.8)13 (3.6)1.7
 UV-B*8 (6.2)18 (7.9)26 (7.3)3.4
 PUVA1 (0.7)14 (6.1)15 (4.2)2.0
Total264 (204.7)496 (216.6)760 (212.3)100


In this study, we tried to demonstrate clinical features of pediatric psoriasis of moderate to severe degree and compare data with those of previously published reports. Although previous studies did not provide much quantitative information about disease severity of their patients,1–6 our results clearly showed that both the disease extent and activity of our patients were more serious compared with other studies. Approximately half of our patients had a severe form of the disease with more than 30% body surface involvement, while two recent studies showed the proportion of pediatric patients with a surface involvement of more than 20% was 3.2%4 and 6.3%,5 respectively. Among various clinical characteristics of pediatric psoriasis, we found some distinctive aspects in our patients compared with previous reports.1–6 Although there could be many factors to elucidate these differences including ethnic differences,18 we thought that the severity could be one of the main reasons.

Regarding general epidemiology, an equal sex distribution was observed, while some previous studies have reported a female preponderance in pediatric psoriasis.2,19 The proportion with a positive family history was similar to other reports.1–6,18 In fact, heritability of pediatric psoriasis differs remarkably depending on studies, ranging 3.6–89%.1–6,18 There was no statistical difference in the prevalence of family history between childhood and adolescent groups, while childhood psoriasis was more serious than adolescent. Our study showed that the mean age of onset was between 10 and 11 years, consistent with some of the previous studies,2,5 while the other studies maintained that onset age was less than 5 years.3,19 These large discrepancies might be partly explained by different referral patterns and services provided from various regions in addition to inherent disease characteristics.

In clinical phenotypes, the proportion of guttate and GPP types was generally higher compared with other studies.1–5 This difference in the distribution of clinical phenotypes might be partly attributed to a more severe disease state of our patients because disease severity of the GPP type was generally serious.20 In fact, 13 of a total of 26 patients with GPP type were admitted to intensive care. In the case of guttate psoriasis, the proportion may be a little overestimated because the morphology of psoriatic lesions was an important diagnostic factor at initial presentation. However, the status of our hospital as a tertiary referral clinic in the nation might also affect the increased proportion of guttate type. The proportion of patients complaining about pruritus was also quite high in our patients, comprising 79.4% of patients. The high prevalence of pruritus might be partly explained by the severe disease state of our patients.21,22 We thought that symptomatic care for pruritus would be essential for pediatric patients with moderate to severe psoriasis. The proportion of nail involvement (22.1%) was compatible with that of other reports.5,6

Regarding body parts affected by psoriasis, we could find a meaningful difference between our patients and those of previous studies.1–6 The relatively lesser involvement of scalp and diaper lesions might be explained by the fact that patients affected in these skin areas generally showed a mild clinical course. The proportion of facial involvement was relatively higher in our patients, consistent with our previous report that facial involvement generally reflects severe psoriasis.23 Regarding external factors influencing disease course, our patients showed similar patterns with those of previous reports.5,24 Therefore, controlling exposure to a certain environment would be partly helpful for these patients.

In addition, we examined all therapeutic methods applied in our patients. The proportions of oral medication and phototherapy were similar to those of previous reports.4,25 However, considering that our patients showed a more severe clinical course,4–6 we thought that systemic therapies should be used only in extreme circumstances. In fact, our group has been relatively prudent in administrating systemic therapies because of the potential side-effects of these therapies. The systemic treatment of pediatric psoriasis has been universally empirical and extrapolated from the reports about adults, as there have been few comparative studies in children. A recent article based on a systematic published work review stated that methotrexate would be considered to be a systematic choice of therapy, while retinoids could be considered in pustular or erythrodermic psoriasis.12 Although clinical trials of biologics have been recently conducted for pediatric patients with moderate to severe degree psoriasis,13,14 they still have a number of limitations in their clinical indications and high prices for ordinary use. Therefore, we thought that more clinical evidences from well-designed clinical trials would be required for the efficacious, optimal regimen and long-term safety of conventional oral medications and phototherapy for pediatric patients.

Finally, because we thought that possible treatment regimens and associated management plans could be different according to patient age within pediatric patients, total patients were divided into childhood and adolescent groups. We could observe guttate, nummular and GPP types more frequently in the childhood group compared with the adolescent group. Mean PASI score, disease activity and pruritus of psoriatic lesions were also significantly more serious in the childhood group. Therefore, we believe that specialized care and treatment plans are highly required.

Despite the limitations of retrospective analysis, our study demonstrated clinical characteristics of pediatric psoriasis in a tertiary referral clinic. Some clinical traits including patterns of clinical phenotypes, disease severity and body parts affected by psoriasis were different from those of previous reports, which could be largely attributed to the more severe disease state of our patients. In addition, we showed that there were differences in clinical characteristics between childhood and adolescent groups. We also found that treatment options were relatively limited considering the severe clinical course of our patients, demanding a need for more research on systemic treatment of pediatric psoriasis.