Crohn's disease (CD) is a chronic disease with a heterogeneous clinical presentation, relapse rate and treatment response. Insufficient control of mucosal inflammation results in irreversible bowel damage and complications and at present no markers are available to predict such a complicated disease course at diagnosis. Therefore, to prevent overtreatment of low risk patients, step-up treatment with subsequent introduction of corticosteroids, thiopurines maintenance and TNF-blockers if a previous category fails is standard care. Combination treatment with thiopurines and a TNF-blocker is more effective than monotherapy but associated with a higher risk for infectious complications. Landmark studies convincingly showed an improved long-term outcome if the TNF-blocker infliximab is introduced early after diagnosis. The standard step-care approach thus prolongs steroid exposure and delays start of disease modifying biologicals in high risks patients. Given the higher efficacy of combination therapy with a thiopurine of infliximab and potential allergic reactions and lower response rates after re-initiation of this chimeric biological, temporary monotherapy with this TNF-blocker has not been studied as first line treatment before. Adalimumab is a humanised monoclonal antibody and subsequently, combination therapy of adalimumab + thiopurines has only a marginal effect on anti-drug anti-body formation. Furthermore, combination therapy with adalimumab does not enhance the clinical response. Therefore, periodic treatment with adalimumab in combination with close monitoring after drug-discontinuation, in newly diagnosed CD might improve outcome, reduce drug-related side effects while still preventing overtreatment.

The aim of this study is to compare the long-term efficacy and safety of periodic adalimumab as initial treatment in newly diagnosed CD patients compared to standard step-care with corticosteroid/budesonide as the initial treatment

Inclusion Criteria:

• Newly diagnosed CD patients or CD patients with a flare, visiting the outpatient clinic or endoscopy ward of the participating centres
• CD diagnosis according to ECCO-guidelines + complete ileo-colonoscopy + complete small bowel imaging at diagnosis (MRI or CT-enterography )
• Naïve to biologicals
• Sufficient knowledge of Dutch language
• 18 years old ≤ 70 years old
• Smartphone with internet access
• Use of myIBDcoach or willingness to start using myIBDcoach

Exclusion Criteria:

• Use of prednisone for longer than 4 weeks in the year before screening
• Use of budesonide (≥6 mg daily) for a duration longer than 3 months in the year before screening
• Use of thiopurines in the 3 years before screening
• Indication for primary treatment with biologicals or surgery
• Malignancy in 5 years before treatment. Exception is adequately treated non-melanoma skin cancer
• Contra-indication for TNF-blockers or immunosuppressive agents
• Contra-indication for MRI- and CT-enterography
• Patients with short bowel syndrome or an ostomy

Data will be made available to other researchers on demand. Patients will be asked to give informed consent to share the collected data with third parties for future research.