Background: Psoriasis, a common inflammatory disease, is associated with atherosclerotic vascular diseases, including stroke, myocardial infarction, and impaired microcirculations, among which circulating microparticles play an important role. In severe psoriasis, there are increased endothelial- and platelet- microparticles that are reduced by TNF-α blockers in parallel with clinical improvement. However, whether Stelara(ustekinumab) treatment would decrease the level of microparticles remains unknown.

Objective: The investigators will evaluate the level of microparticles among normal control, severe psoriasis before and 4 months after ustekinumab treatment.

Methods: The investigators will recruit 50 patients with severe psoriasis who received ustekinumab and 50 control subjects without psoriasis from August 2014 to July 2016. Concentrations of microparticles with expression for surface markers (Annexin V, CD31, and CD41a) will be measured in peripheral blood using flow cytometry.

Inclusion Criteria:

• Patients with severe psoriasis who receive ustekinumab treatment.
• Patients in the control group are examined thoroughly to make sure no psoriatic lesions by two dermatologists. Age, sex, lipid profiles, and blood pressure are recorded for all subjects.

Exclusion Criteria:

• The psoriatic patients and healthy controls who have pregnancy or infection (such as tuberculosis or sepsis) are excluded.