Clinicopathologic Spectrum and Oxford MEST-C Scores in Adult IgA Nephropathy in Middle Eastern Cohorts: A PRISMA-Guided Literature Review With Crude Pooled Lesion Frequencies

TL;DR

This study reviews IgA nephropathy in Middle Eastern adults, finding common kidney lesions and highlighting the need for better regional data.

Contribution

The study provides pooled lesion frequencies for IgA nephropathy in Middle Eastern cohorts, revealing patterns and limitations in regional histologic data.

Findings

Mesangial hypercellularity (M1) was present in 80.0% of cases.

Tubulointerstitial scarring (T1-2) occurred in 56.4% of patients.

Crescent formation (C≥1) was reported in ~27.6% of cases.

Abstract

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide, but Middle Eastern adults are under-represented in cohorts reporting Oxford MEST-C (mesangial, endocapillary, segmental, tubular atrophy/interstitial fibrosis, and crescent) lesions, limiting region-specific histologic risk profiling. We performed a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-guided systematic review of observational adult (≥18 years) primary IgAN cohorts from Middle Eastern countries reporting Oxford MEST or MEST-C. MEDLINE (PubMed), Embase, and Scopus were searched from January 1, 2009, to November 24, 2025, with no language restrictions; citation searching (backward reference screening and forward citation tracking) was also performed. Two reviewers independently screened studies, extracted data, and assessed risk of bias using the Newcastle-Ottawa Scale (NOS). For each MEST-C component, we calculated descriptive pooled proportions by summing numerators and denominators across cohorts with available extractable data; renal outcomes were synthesized narratively. Four retrospective cohorts (total n=528) from Iran, Turkey, and Saudi Arabia met eligibility criteria. Three cohorts contributed extractable lesion counts for M1, S1, and T1-2 (E1 data were available in two cohorts). Descriptive pooled frequencies were: mesangial hypercellularity (M1) 80.0%, endocapillary hypercellularity (E1) 35.7%, segmental glomerulosclerosis (S1) 58.5%, and tubulointerstitial scarring (T1-2) 56.4%. Crescent reporting was limited; where extractable, C≥1 was 28.9% in the Turkish cohort, and a sensitivity approximation incorporating a study reporting overall crescent frequency yielded ~27.6%. Where reported, T and crescent lesions were associated with worse renal outcomes. Formal heterogeneity testing and quantitative outcome meta-analysis were not performed due to a few clinically diverse cohorts. Risk of bias was low-to-moderate, mainly due to retrospective design, convenience sampling, and incomplete outcome reporting. Available Middle Eastern cohorts show frequent M1 and S1, with substantial T1-2 scarring and crescents in a sizeable minority of biopsied patients. These findings likely reflect advanced histologic injury at biopsy in tertiary-care cohorts and/or variation in case mix and biopsy/referral practices, underscoring the need for prospective regional registries with standardized pathology reporting and outcome definitions.

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