• The primary outcomes are to further evaluate the safety of ustekinumab in patients with moderate to severe plaque psoriasis and to further evaluate the safety of infliximab in patients with chronic severe (extensive and/or disabling) plaque psoriasis. [ Time Frame: 8 years from last patient enrolled ] [ Designated as safety issue: Yes ]
  

• To characterize disease features in patients exposed to ustekinumab and/or infliximab [ Time Frame: every 6 months for 8 years ] [ Designated as safety issue: No ]
  
• To evaluate clinical outcomes, quality of life, and comorbidities for patients who may receive conventional systemic or biologic therapy for psoriasis [ Time Frame: every 6 months for 8 years ] [ Designated as safety issue: No ]
  
• To assess the proportion of patients exposed to ustekinumab who meets labeling criteria relative to the number of patients exposed, based on the data collected within the registry [ Time Frame: every 6 months for 8 years ] [ Designated as safety issue: No ]
  
• To assess the proportion of patients exposed to infliximab who meets labeling criteria relative to the number of patients exposed, based on the data collected within the registry [ Time Frame: every 6 months for 8 years ] [ Designated as safety issue: No ]
  

PSOLAR is an 8-10 year registry study. A registry is an observational study that evaluates the status of a disease. This registry study will only include patients who volunteer to take part. About 4000 infliximab-exposed patients and 4000 ustekinumab-exposed patients as well as a comparable number of patients (4000) on other standard of care psoriasis therapies (e.g. Etanercept) and/or psoriasis treatments (e.g. topical or light therapy treatments) will take part in the registry study, internationally. The Registry does not require any study-specific testing, but may capture test information (e.g. laboratory tests, X-rays) that are collected as part of normal routine care for the registry program. Patient information will be collected at the enrollment visit and about every 6 months thereafter. At enrollment, information on demographics (e.g. gender, race, date of birth), medical history and family medical history, details of past and current psoriasis treatments (e.g. infliximab and standard therapy), and current medication regimens will be collected. Clinical follow-up will be based on observations from physical examination, clinical disease status, Quality of Life assessment (e.g. Dermatology Life Quality Index, Hospital Anxiety and Depression Scale, EQ-5D (EuroQoL-5D is a Quality of Life Questionnaire) Health Questionnaire Scale, Employment/Productivity Health Economic Questionnaire), current medications, and any adverse events/problems reported. During each six -month follow-up visit with the study doctor, information collected will include observations from physical examination, updates on clinical disease status, Quality of life assessments, medications and adverse events/problems. No study agents will be administered in this registry. All patients will receive standard of care treatments prescribed by the patient's physician.