Rethinking spondyloarthritis: beyond lumping and splitting.

Purpose of review: The classification of spondyloarthritis (SpA) has long been debated, with ongoing discussions about whether to "lump" various subtypes together or "split" them into smaller distinct disease categories. This review explores the evolution of the SpA concept and discusses novel approaches that move beyond traditional models of SpA classification.

Recent findings: Since its introduction in the 1970s, the SpA concept has undergone substantial modifications, incorporating advances in genetics, imaging, and clinical research. The recognition of axial and peripheral SpA as distinct yet overlapping entities has reshaped classification and drug approval processes. Data-driven methodologies have provided new insights into disease heterogeneity. Recent research highlights the limitations of traditional classification systems, emphasizing the need for unbiased approaches that integrate clinical and molecular features.

Summary: Current historically derived classification paradigms for SpA are largely based on clinical phenotype and fail to capture the full spectrum of disease heterogeneity. Defining SpA subsets by incorporating genetic and immunological characteristics may improve diagnostic precision and improve outcomes. Future research should focus on refining classification frameworks across the entire clinical spectrum of SpA to improve patient stratification, guide treatment decisions, and address existing gaps in SpA care.