Primary intestinal lymphangiectasia across the lifespan: adult–pediatric comparisons of diagnostic delay, immune findings, and treatment patterns

Background: Primary intestinal lymphangiectasia (PIL) is classically considered a pediatric lymphatic disorder, but adult presentation may be under-recognized. Methods: We searched six databases from inception through January 31, 2026, for reports with extractable PIL data. Adult–pediatric comparisons used Mann–Whitney U and Fisher exact tests. Results: After a source-level and eligibility audit, the evidence base comprised 128 individually abstracted primary PIL cases and two author-described pediatric cohorts reported only in aggregate (n = 28 and n = 34); both aggregate cohorts were summarized separately. Among 111 individual cases with age at diagnosis, 58 (52.3%) were adults and 53 (47.7%) were pediatric. Median diagnostic delay was 4.00 years in adults (IQR, 1.00–15.00; n = 30) and 2.21 years in pediatric cases (IQR, 0.69–6.56; n = 30; p = 0.135); delays of at least 10 years occurred in 10/30 (33.3%) and 3/30 (10.0%), respectively (p = 0.057). Baseline albumin was 1.90 g/dL (IQR, 1.60–2.20; n = 93). Individually mapped objective protein-losing enteropathy testing was documented in 37/128 (28.9%), lymphocyte subsets in 20/128 (15.6%), and follow-up duration in 80/128 (62.5%). Diet and medium-chain triglycerides predominated; no estimable treatment or recurrence comparison reached nominal significance. Conclusions: Adult PIL is well represented in published individual cases, but selective reporting and incomplete diagnostic confirmation limit inference. Structured exclusion of secondary etiologies and standardized longitudinal outcomes are needed.