Shared Pathways Between Non-Alcoholic Fatty Liver Disease and Psoriatic Disease With Guselekumab Therapy

Inclusion criteria: * Adults with a diagnosis of PsA fulfilling the classification for PsA (CASPAR) criteria. * Overweight or obese by BMI ≥ 25.0 kg/m2 or ≥ 23.0 for Asian participants * Patients are starting Guselkumab therapy as indicated by primary rheumatologist * Elevated liver fat on controlled attenuation parameter (CAP) ≥ 288 dB/m, which is consistent with NAFLD after exclusion of secondary causes of liver disease8. Exclusion Criteria: * Evidence of other causes of chronic liver disease * Hepatitis B as defined as presence of hepatitis B surface antigen (HBsAg). * Previous or current infection with Hepatitis C as defined by presence of hepatitis C virus Ab in serum (anti-HCV Ab). * Autoimmune hepatitis as defined by anti-nuclear antibody (ANA) of 1:160 or greater and liver histology consistent with autoimmune hepatitis or previous response to immunosuppressive therapy. * Autoimmune cholestatic liver disorders as defined by elevation of alkaline phosphatase and anti-mitochondrial antibody of greater than 1:80 or liver histology consistent with primary biliary cirrhosis or elevation of alkaline phosphatase and liver histology consistent with sclerosing cholangitis. * Wilson disease as defined by ceruloplasmin below the limits of normal and liver histology consistent with Wilson disease. * Alpha-1-antitrypsin deficiency as defined by alpha-1-antitrypsin level less than normal and liver histology consistent with alpha-1-antitrypsin deficiency. * Hemochromatosis as defined by presence of 3+ or 4+ stainable iron on liver biopsy and homozygosity for C282Y or compound heterozygosity for C282Y/H63D. * Drug-induced liver disease as defined on the basis of typical exposure and history. * Bile duct obstruction as shown by imaging studies. * History of gastrointestinal bypass surgery or ingestion of medications known to produce steatosis, such as corticosteroids, high-dose estrogen, tamoxifen, amiodarone, or tetracycline in the previous 6 months. * Evidence of cirrhosis or previously known cirrhosis based on the results from a previous liver biopsy or history of portal hypertension presented by ascites, hepatic encephalopathy, or varices * Presence of regular and/or excessive use of alcohol (defined as \>30g/day for males and \>15g/day for females) for a period longer than 2 years at any time in the last 10 years * The subject is a pregnant or nursing female * History of known HIV infection