Multi-Omic SignAtures of Inflammatory Cutaneous Diseases

MOSAIC (Multi-Omic Signatures of Inflammatory Cutaneous Diseases) is a non-commercial, investigator-led, single-centre, prospective observational cohort study. Participants will be recruited at Guy's and St Thomas' NHS Foundation Trust, with University Hospitals Birmingham acting as a participant identification centre. The study will investigate individuals with a broad range of common and rare inflammatory skin diseases, including genetic skin diseases such as epidermolysis bullosa, alongside a healthy comparison cohort.

The study is based on the hypothesis that inflammatory skin diseases may share identifiable molecular and immune pathways, despite differences in their clinical presentation and underlying causes. By integrating molecular data with detailed clinical information, MOSAIC aims to identify and characterise disease-associated immune signatures, distinguish molecular subgroups or "endotypes", and identify potentially druggable pathways. The study will also investigate how molecular and immune profiles change following systemic treatment and will establish a well-characterised biological resource for future skin disease research. MOSAIC is observational: no treatment will be assigned or administered as part of the study, and participants will continue to receive clinical care according to usual practice.

Participants will undergo a detailed baseline assessment. Clinical information will include demographic characteristics, medical and family history, disease phenotype and duration, previous and current treatments, concomitant conditions and medications, relevant environmental factors, clinical assessments, patient- and clinician-reported information, and medical photography where applicable. Healthy participants will provide comparison data and samples at a single baseline visit.

Biological samples collected at baseline may include routine clinical blood samples, research blood samples and skin biopsies. Research blood will be used to isolate DNA, RNA, serum, plasma and peripheral blood mononuclear cells. Patients may provide samples from lesional and non-lesional skin, while healthy participants will provide site-matched control samples where possible. Subject to separate consent and clinical relevance, optional samples may include skin or mucosal swabs, stool, mucosal biopsies, scalp biopsies and skin that would otherwise be discarded during surgery. Relevant historical results obtained within six months before the baseline visit may be used where scientifically and clinically appropriate to reduce unnecessary repeat invasive procedures.

Patients who start, switch or stop a systemic therapy, or who experience a worsening of their disease, may be invited to attend optional longitudinal follow-up visits if they are not participating in another interventional study. Up to five optional follow-up visits may take place at clinically and scientifically relevant time points, such as Day 3, Week 1, Week 16, Month 6 and Month 12. The timing may be adapted according to the mechanism of the treatment or the specific research question. Follow-up assessments may include updated clinical and treatment information, examination, disease-specific assessments, medical photography and repeat collection of research samples. This will allow molecular profiles before and after treatment, or during changes in disease activity, to be compared. Clinical outcome information may be followed for up to five years after sampling to support longer-term correlation with molecular findings.