rs28929454 — SERPINA1

SERPINA1 rs28929454 — A Mortality-Associated ANCA Vasculitis Variant

Alpha-1 antitrypsin (AAT), encoded by SERPINA1, is the body's principal serine protease inhibitor¹¹ serine protease inhibitor
AAT is produced in the liver and secreted into the bloodstream, where it neutralizes neutrophil elastase and Proteinase 3 (PR3) released during inflammatory episodes. The rs28929454 variant is an intronic SERPINA1 polymorphism that has been identified as a significant predictor of mortality in patients with ANCA-associated vasculitis (AAV)²² ANCA-associated vasculitis (AAV)
AAV encompasses granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic GPA — rare but serious autoimmune conditions causing necrotizing inflammation of small blood vessels. The variant is in very strong linkage disequilibrium with the established AAV risk allele rs7151526 (r²=0.88), suggesting both tag the same functional regulatory signal in the SERPINA1 locus.

The Mechanism

SERPINA1 encodes AAT, whose primary immune function is to neutralize Proteinase 3 (PR3), the major autoantigen in PR3-ANCA granulomatosis with polyangiitis. When AAT function is reduced — whether by coding deficiency variants (like the Z allele, rs28929474) or by regulatory variants that reduce SERPINA1 expression or mRNA stability — PR3 remains uninhibited on neutrophil surfaces. Exposed, uninhibited PR3 drives formation of anti-PR3 ANCA autoantibodies. These antibodies then activate more neutrophils in a self-amplifying inflammatory loop, causing the necrotizing vasculitis characteristic of GPA.

The rs28929454 variant falls within an intronic region of SERPINA1. Its exact molecular mechanism has not been independently characterized; however, its tight co-segregation with the downstream regulatory variant rs7151526 (r²=0.88) suggests both variants may tag a common regulatory haplotype affecting SERPINA1 expression or post-transcriptional mRNA processing. Intronic variants can influence splicing enhancer sequences, affect co-transcriptional folding, or alter lncRNA expression from overlapping transcripts — all mechanisms by which a non-coding variant could modulate AAT output and tip the protease-antiprotease balance toward autoimmune inflammation.

The Evidence

The primary evidence comes from a 2024 prospective cohort study of 115 Brazilian AAV patients³³ 2024 prospective cohort study of 115 Brazilian AAV patients
Giardini et al., Clinics (São Paulo), 2024 that examined two SERPINA1 polymorphisms — rs7151526 and rs28929454 — as potential predictors of disease outcome. The finding was striking: rs28929454 carriers had a mean survival of 54.9 years (95% CI: 40.9–68.9), compared to 68.0 years for non-carriers (p < 0.0001) — a potential reduction of more than 13 years in disease-affected survival. In multivariate Cox regression, SERPINA1 polymorphisms were identified as the most significant predictor of mortality in the cohort (HR = 6.2, 95% CI 1.4–27.1, p = 0.015). Of the two variants tested, rs28929454 showed a more pronounced survival signal than rs7151526 (which showed mean survival 57.4 years).

Supporting biological context comes from studies of the linked variant rs7151526: a meta-analysis of 18 studies⁴⁴ meta-analysis of 18 studies
Banerjee et al., International Journal of Rheumatic Diseases, 2022 confirmed the rs7151526-A allele — which co-segregates with rs28929454 at r²=0.88 — as a predisposing allele for GPA (Meta-OR = 2.70, 95% CI 1.51–4.85, p = 0.0008). Given the strong LD, rs28929454 likely tags the same functional signal.

Important caveat: rs28929454 has not yet been indexed in dbSNP or Ensembl as a standalone variant entry. The full molecular characterization of this variant (precise chromosomal position, reference allele, functional consequence) has not been independently verified against a public genomic reference. The allele frequencies and strand assignment shown here are inferred from the linked rs7151526 entry and should be updated when the variant is characterized in public databases.

Practical Actions

Carrying the risk allele at rs28929454 does not mean you will develop ANCA vasculitis — the disease affects approximately 3 per 100,000 people per year, and environmental triggers are required. However, the survival data from the Giardini cohort suggest that when AAV does occur in carriers, the clinical course is significantly more aggressive. Early recognition and prompt specialist referral are therefore especially important.

AAV characteristically presents with upper respiratory symptoms (persistent sinusitis, nosebleeds, subglottic stenosis in GPA), lower respiratory disease (cough, hemoptysis), kidney involvement (hematuria, proteinuria, rising creatinine), and systemic features (fever, weight loss, night sweats). Prompt ANCA testing (PR3-ANCA and MPO-ANCA) at symptom onset can enable treatment before irreversible organ damage occurs.

Interactions

rs28929454 is in very tight LD (r²=0.88) with rs7151526, a well-characterized 3'-regulatory SERPINA1 variant with established GPA risk data. The two variants co-segregate on the same SERPINA1 haplotype background. Understanding which of these variants is functionally causal — or whether both contribute independently — requires fine-mapping studies not yet published.

The broader SERPINA1 deficiency context includes the Z allele (rs28929474, p.Glu342Lys) — the most common coding deficiency allele — and the S allele (rs17580, p.Glu264Val). These coding variants cause quantitative AAT deficiency with their own GPA associations (the Z allele alone has Meta-OR=12.60 for GPA in the Banerjee 2022 meta-analysis). Carrying rs28929454 alongside a classical deficiency allele (MZ or SZ phenotype) would likely compound risk, though direct data on combined genotype effects are not available.