This prospective observational study aims to evaluate plasma intestinal fatty acid-binding protein (I-FABP) levels in children with IgA vasculitis and investigate their association with gastrointestinal involvement. Blood samples will be collected at diagnosis and during follow-up 2-4 weeks later. The study will assess the potential value of plasma I-FABP as a biomarker for gastrointestinal involvement in pediatric IgA vasculitis.

This prospective observational cohort study aims to evaluate the association between plasma intestinal fatty acid-binding protein (I-FABP) levels and gastrointestinal involvement in children with IgA vasculitis (Henoch-Schönlein purpura).

Children aged 2-18 years who fulfill the EULAR/PRINTO/PRES classification criteria for IgA vasculitis will be enrolled. Clinical, laboratory, and demographic data will be collected at diagnosis (baseline). Participants will be followed prospectively, and a second assessment will be performed during the routine follow-up visit at approximately 2-4 weeks after diagnosis.

Blood samples will be obtained at baseline and during follow-up. Plasma will be separated and stored for subsequent measurement of I-FABP levels. The primary objective is to determine whether plasma I-FABP levels are associated with the presence of gastrointestinal involvement in pediatric IgA vasculitis.

Participants will be classified according to the presence or absence of gastrointestinal involvement. Clinical manifestations, laboratory findings, and plasma I-FABP levels will be compared between groups. The study does not involve administration of investigational drugs, devices, or therapeutic interventions. All procedures are performed as part of routine clinical follow-up with additional blood sampling for biomarker analysis.

The findings may help identify noninvasive biomarkers for the early detection and assessment of gastrointestinal involvement in children with IgA vasculitis.

Inclusion Criteria:

• Diagnosis of IgA vasculitis (Henoch-Schönlein purpura) according to EULAR/PRINTO/PRES classification criteria.
• Age between 2 and 18 years.
• Availability for blood sample collection at diagnosis (baseline visit).
• Ability to attend a routine follow-up visit approximately 2-4 weeks after diagnosis.
• Parent or legal guardian able and willing to provide written informed consent.

Exclusion Criteria:

• Refusal of informed consent by the parent/legal guardian.
• Inability to obtain a baseline blood sample.
• Inability to complete study follow-up procedures.

Children aged 2-18 years with newly diagnosed IgA vasculitis who are followed at a tertiary pediatric rheumatology center. Participants will be prospectively evaluated for gastrointestinal involvement and plasma I-FABP levels at diagnosis and during routine follow-up approximately 2-4 weeks later.

Individual participant data will not be shared in order to protect participant privacy and confidentiality.