Primary Immunodeficiency and Enteropathy: A Diagnostic and Therapeutic Challenge

Introduction Inborn errors of immunity (IEIs) frequently present with gastrointestinal manifestations, yet enteropathy remains a poorly characterized complication with debilitating sequelae. Often misdiagnosed as atypical coeliac disease or inflammatory bowel disease (IBD), primary immunodeficiency (PID)-associated enteropathy (PID-E) lacks specific diagnostic endoscopic or histological criteria. This review explores distinctions between PID-E and classic gastrointestinal (GI) diseases and outlines our national initiative to develop a clinical database of affected patients. Method We conducted a comprehensive review of peer-reviewed articles, registries, and case series describing GI manifestations in PIDs, focusing on immune-mediated mechanisms, diagnostic features, and immunosuppressive treatments. Concurrently, we distributed an expression of interest Google Survey via the Clinical Immunogenomics Research Consortium of Australasia (CIRCA) to estimate case numbers nationally. Exclusion criteria included self-limited GI infections (<8 weeks), IBD diagnosed before the age of 6, and GI disease related to chronic granulomatous disease (CGD), X-linked inhibitor of apoptosis protein (XIAP) deficiency, and immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome. Results PID-E is loosely defined as chronic diarrhoea with malabsorption and small bowel inflammation not meeting diagnostic criteria for classic GI diseases. Histology is variable and often non-specific, including villous atrophy, intraepithelial lymphocytosis, graft-versus-host disease-like changes, and IBD-like inflammation, but commonly a notable absence of plasma cells. Diagnosis requires integration of clinical, histological, and immunological data. Optimal treatment has not been defined; however, biologic agents, including anti-TNF-alpha agents, CTLA-4 inhibitors, and mTOR inhibitors, have shown benefit in case reports. Our national survey yielded 20 responses, identifying an estimated 100–150 cases across Australia to date, contributing to a growing database to inform future research and clinical guidelines. Conclusion PID-E is a distinct clinical entity that requires early recognition and tailored management approach through multidisciplinary collaboration. Our multi-centre data collection highlights the heterogeneity of presentations, complications, and treatment in Australian patients with PID-E. There is a need for consensus guidelines and a national database to drive future research and improve patient outcomes.