This study will assess differences in inflammatory proteins, lipoprotein composition, cholesterol efflux and HDL-proteome in moderate-to-severe pediatric psoriasis who at baseline begin systemically administered therapy vs: a) healthy controls; and b) patients with milder psoriasis.

Inclusion Criteria:

• Children ages 6-17 years of all races/ethnicities with plaque and/or extensive guttate psoriasis for at least 6 months and on topical or systemic therapy
• Patients in the systemic group can be starting a medication for the first time OR transitioning from another systemic if unresponsive and on that previous treatment for ≤ 3 months.
• Patients may concurrently have psoriatic arthritis if initiation of a systemic medication is warranted by skin severity.
• Children ages 6-17 years of all races/ethnicities with acne being treated with isotretinoin
• Children ages 6-17 years of all races/ethnicities without plaque or guttate psoriasis and history of severe acne or treatment with isotretinoin as controls.

Exclusion Criteria:

• Patients less than 6 years of age or 18 years and older
• Patients with congenital heart disease, prior cardiac catheterizations/surgeries, or on cardiac medications in the past two years other than for hypertension (eg, calcium channel-blockers, beta-blockers and vasotropic medications).
• Patients who have other systemic inflammatory diseases (including atopic dermatitis, severe acne, inflammatory bowel disease, juvenile idiopathic arthritis, connective tissue diseases and/or other autoimmune diseases).
• Patients who have active infection or malignancy or have suffered from infection requiring oral or parenteral antibiotic in past 2 weeks.
• Patients and parents/caregivers unable to give written informed consent.

The investigators plan to recruit approximately 120 subjects total. Subjects will be divided into 4 groups: i) patients to be treated only topically (n=30); ii) patients with moderate-to-severe psoriasis who begin systemic treatment (n=30; ~15 DMARDs and 15 biologics); iii) age-, sex- and BMI percentile-matched controls (n=30); iv) patients being treated with isotretinoin for acne (n=30).