Handeczema is a common chronic skin disease that markedly affect health and quality of life. Effective treatment is limited by the lack of biomarkers that can predict disease course, comorbidities and treatment response. This study is is an observational, prospective, study of patients initiating treatment with methotrexat at the Department of Dermatology and Allergy at Herlev- and Gentofte Hospital.

The main aim is to study the clinical effect of methotrexat in patients with hand eczema. Secondary aims are to study drug survival, reasons for termination of treatment and side effects.

The Copenhagen Translational Skin Immunology Biobank and Research Programme (BIOSKIN) is a prospective translational biobank and research study designed to recruit 3,000 patients with atopic dermatitis, allergic contact dermatitis or psoriasis over at least five years. The open longitudinal study design allows participants to enter and leave the cohort at time points that reflect their natural disease and treatment course. At each study visit, investigators collect biological samples, conduct structured interviews, and obtain patient-reported outcomes on disease-specific and general health-related factors.

In this study of patients initiating treatment with methotrexat because of hand eczema, patients are assessed with clinical assessments including dermatologist-verified diagnose, evaluation of disease severity, and detailed phenotyping. Examinations are performed before and after initiation of methotrexat as a tablet or as subcutaneous injections, and at least annually.

Longitudinal modelling will enable detailed characterisation of the patiens and disease trajectories and treatment responses. The aim is to improve understanding of the effect and sideeffects of methotrexat in a cohort of hand eczema patients with moderate to severe disease.

Inclusion Criteria:

• Individuals of any age with psoriasis, atopic dermatitis, contact dermatitis, or other inflammatory skin diseases.
• Patients seen at the Department of Dermatology and Allergy, Herlev and Gentofte Hospital, or recruited through public advertisement.
• Ability to provide informed consent (parent/guardian for minors).
• Healthy volunteers

Exclusion Criteria:

• Inability or unwillingness to provide informed consent.
• Any condition that, in the investigator's judgment, makes participation inappropriate or unsafe.

Department of Dermatology and Allergy, Herlev and Gentofte Hospital,

Individual participant data (IPD) will not be shared due to restrictions under the Danish Data Protection Act and related regulations, which do not permit the disclosure of identifiable or potentially identifiable health data to external parties.