Tattoo Inflammation With Uveitis: From Recognition to Definition.

Tattoo inflammation with uveitis (TIU) is increasingly recognised but growing case numbers have revealed substantial heterogeneity. Patients currently classified as TIU appear to include those with overt or evolving systemic sarcoidosis as well as those with isolated, pigment-associated ocular inflammation. Recognition has therefore outpaced case definition. Phenotypic imprecision has clinical and scientific implications. Sarcoidosis-associated TIU warrants multidisciplinary evaluation and longitudinal surveillance, whereas other presentations may reflect a localised pigment-driven immune response. In rare conditions such as TIU, even modest cohort heterogeneity can obscure reproducible biological signals and impede mechanistic understanding. Recurring clinical patterns suggest distinct TIU phenotypes, with emerging translational data providing preliminary biological support for these distinctions. We therefore propose a classification framework comprising three groups: TIU-R (restricted), TIU-S (sarcoidosis-associated), and TIU-U (undifferentiated), intended to support consistent reporting, appropriate multidisciplinary referral, and coherent translational investigation. Establishing robust case definitions now will be foundational for future clinical and mechanistic research.