BACKGROUNDThe prevalence of childhood psoriasis is estimated at between 0.4% and 0.7%. Clinical aspects of the diseases depend on age. The aim of this study was to investigate the clinical aspects of psoriasis according to age and sex.PATIENTS AND METHODSA cross-sectional, multicentre study of children with psoriasis was performed by investigators belonging to the Research Group of the French Society of Paediatric Dermatology. The study was conducted from April 2012 to March 2013. Inclusion criteria were age less than 18 years and clinical diagnosis of psoriasis. The children were classified into 3 groups by age: infants: <2 years; children: ≥2 years and <13 years; adolescents≥13 years. The information collected included demographic data, clinical, epidemiological, and therapeutic aspects of the psoriasis, as well as analysis of comorbidities.RESULTSThree hundred and thirteen children were included: 27 (8.6%) infants, 207 (66.1%) children, and 79 (25.2%) adolescents. Plaque psoriasis was the most frequent clinical type of psoriasis seen in children and adolescents (>41%), but it accounted for only 25.9% of psoriasis of infants (P<0.0001). Napkin psoriasis (37.0%) and inverse psoriasis (22.2%) were the most common forms of psoriasis seen in infants and were described significantly more frequently in this group than in the two other groups (P<0.003). Nail involvement was more common in adolescents (37.2%, P=0.03) and children (32.9%) than in infants (14.8%) and affected boys more than girls (43.6% vs 22.0%, P<0.0001). Girls presented scalp psoriasis more frequently (17.7% vs 8.7%, P=0.02). Local vitamin-D treatment and systemic therapies were used more frequently in children and adolescents than in infants. There was no significant difference for treatment use, including for acitretin, according to gender.DISCUSSIONPlaque psoriasis was the most common clinical type of psoriasis in children but affected less than 50% of the children. Age had a significant impact on extra-cutaneous skin disorders and on treatment used, while sex had little incidence. The frequency of comorbidities was not affected by age.CONCLUSIONChildhood psoriasis thus presents specific characteristics dependent on the age of the child. The results of studies exclusively dealing with adults cannot be extrapolated to children.