While methotrexate (MTX) remains a treatment of choice for patients with rheumatoid arthritis (RA), psoriasis (PsO) and psoriatic arthritis (PsA), long-term MTX use has been shown to be associated with liver fibrosis and cirrhosis in these patients. In addition, gut dysbiosis has been found to be associated with liver fibrosis and cirrhosis via the gut-liver axis, underscoring the potential role of gut microbiota and bacterial translocation in the pathogenesis of chronic liver diseases in these patients.

In this study, we aim to assess the prevalence of advanced liver fibrosis or cirrhosis among these patients on MTX treatment compared to those without, using transient elastography. We also aim to identify the possible risk factor(s) for advanced liver fibrosis or cirrhosis among them. Further, we aim to characterize the difference in fecal microbiota patterns among these three groups of patients.

Using a cross-sectional, prospective cohort design, this study will enroll approximately 600 eligible patients, including 300 patients with PsO/PsA and 300 patients with RA, to examine the following hypotheses:

1. Patients on higher cumulative dose of MTX will have higher prevalence of advanced liver fibrosis or cirrhosis compared to those on lower cumulative dose of MTX;
2. Patients with MTX use will have higher prevalence of advanced liver fibrosis or cirrhosis compared to those without MTX use;
3. The fecal microbiota composition will be different between patients with and without MTX treatment; and
4. The fecal microbiota composition will be different between patients with and without advanced fibrosis/cirrhosis while on MTX treatment.

Inclusion Criteria:

• Age between 18 to 85 years
• Have regular follow up in Dermatology/ Rheumatology clinics of Queen Mary Hospital
• Diagnosed with PsO/PsA or RA
• Chinese ethnicity

Exclusion Criteria:

• Age below 18 years or above 85 years
• Known decompensated cirrhosis
• Pregnancy or breastfeeding
• Unstable medical illness or active infection
• Unable to provide written consent
• Unable to adhere to the protocol
• Unable to read and/or write Chinese language
• On anticoagulant/ antiplatelet treatment
• Abnormal platelet count <150
• Known disease/condition with prolonged INR/bleeding tendency

All patients who have regular follow up in Dermatology/ Rheumatology clinics of Queen Mary Hospital, with a diagnosis of PsO/PsA and/or RA will be identified and screened for eligibility.