All Participants diagnosed with moderate to severe plaque psoriasis who will either start therapy with ustekinumab within 2 months after the first assessment in the study or have started therapy with ustekinumab in the 12-week period before the first assessment in the study as per routine clinical practice, will be monitored for the long-term safety of ustekinumab and long-term effects of ustekinumab on growth and development. The primary data source for the study will be the medical records of participants and standardized questionnaires (completed by the physician and by the participant/parent).

Participants will not receive any intervention as part of this study. Participants with moderate to severe plaque psoriasis who are initiating treatment with ustekinumab in clinical practice (patients should either start therapy with ustekinumab within 2 months after the first assessment in the study or have started therapy with ustekinumab in the 12-week period before the first assessment in the study for the treatment of psoriasis) will be observed for the long-term safety of ustekinumab and the long-term effects of ustekinumab on growth and development.

An adverse event is any untoward medical occurrence in a patient administered a medicinal product. An adverse event does not necessarily have a causal relationship with the treatment. An adverse event can be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product, whether or not related to that medicinal product.

All participants will be monitored for the long-term safety of ustekinumab for the frequency and severity of adverse events potentially related to immune modulation and of clinical interest such as: serious infections, malignancies, and autoimmunity.

Growth will be based on height recorded at baseline and throughout the observational period.

Growth will be based on body weight recorded at baseline and throughout the observational period.

Growth will be based on body weight recorded at baseline and throughout the observational period. Sex and age adjusted BMI will be calculated by dividing the body weight (in kilograms) by the square of height (in meters).

The Tanner scale is used to measure visible changes during puberty commonly referred to as "Tanner stages". It has 3 components: breasts/genitalia, pubic hair, and growth. Female participants are evaluated for breast development and pubic hair distribution and male participants are evaluated for development of external genitalia and pubic hair distribution, based on a 5-stage ordinal scale ranging from TS 1 (prepubertal/preadolescent characteristics) to TS 5 (mature or adult characteristics).

The PASI is a measure for assessing and grading the severity and extent of psoriatic lesions and their response to therapy. The PASI measure also accounts for body surface area of psoriasis involvement. In the PASI measure, the body is divided into 4 regions: the head, trunk, upper extremities, and lower extremities. Each of these areas is assessed separately for erythema, induration and scaling, which are each rated on a scale of 0 to 4. Total PASI score ranges from 0 to 72. A PASI 50 response represents at least 50 percent improvement from baseline in the PASI score.