Inclusion Criteria:  Newly diagnosis of rheumatoid arthritis (RA), reactive arthritis (ReA), ankylosing spondylitis (AS), psoriatic arthritis (PsA), psoriasis (Ps), gouty arthritis (GA), hidradenitis suppurativa (HS), pulmonary sarcoidosis (PSar), Crohn's disease (CD), or ulcerative colitis (UC). Treatment-naïve which is defined as no current or previous disease-modifying anti-rheumatic drugs or systemic immunosuppressive drugs including glucocorticoids. Presence of treatment indication (no contra-indications) and patient accept to start first-line treatment in accordance with the Danish national guideline for the specific diagnosis following the baseline visit.  Exclusion Criteria:  Coeliac disease, food allergy or severe food intolerance. Current cancer. Hepatitis B and C, HIV, HTLV1/2, and active TB or other serious chronic infections. Pregnant or breastfeeding women. Not wishing to participate or not suited for FMT intervention or project evaluation.