rs1898671 — TSLP TSLP Intronic Variant (Atopic Dermatitis)

TSLP rs1898671 — A Genetic Dial on Atopic Dermatitis Severity

Atopic dermatitis affects up to 20% of children and persists into adulthood in roughly a third of cases. What determines whether a child's eczema resolves within a few years or becomes a lifelong burden? Part of the answer lies in a single intronic variant in the TSLP gene on chromosome 5. The rs1898671 T allele is consistently associated with milder, shorter-lived atopic dermatitis — a genetic factor that predicts disease trajectory well before a child sees their first dermatologist.

TSLP (thymic stromal lymphopoietin) is a cytokine¹¹ cytokine
A small signaling protein secreted by immune and epithelial cells to coordinate inflammatory responses produced primarily by keratinocytes in the skin barrier. When the skin is breached — by allergens, irritants, or filaggrin loss-of-function mutations — keratinocytes release TSLP as an alarmin²² alarmin
An "alarm signal" molecule released by stressed or damaged cells to activate innate and adaptive immunity that instructs dendritic cells and innate lymphoid cells to drive a Th2-skewed inflammatory response. This cascade — TSLP → dendritic cell activation → Th2 polarization → IL-4/IL-13/IL-31 production — is the central pathway in atopic dermatitis pathogenesis. Genetic variation at rs1898671 appears to modulate baseline TSLP output or activity, setting the gain on this entire signaling chain.

The Mechanism

rs1898671 is located within intron 1 of TSLP on chromosome 5q22.1 (GRCh38 position 111,072,304), approximately 2 kb from the transcription start site. It does not change any amino acid in the TSLP protein; instead, it likely affects intronic regulatory elements³³ intronic regulatory elements
Introns contain enhancers, silencers, and splice-site sequences that modulate how much mRNA is produced from a gene that control TSLP expression levels or alternative isoform splicing. TSLP exists as two isoforms: a short form with antimicrobial properties and a long form that drives type 2 allergic inflammation. The intronic position of rs1898671 is consistent with a role in regulating this isoform balance or baseline transcription rate.

The net result: T allele carriers appear to produce or signal through less inflammatory-isoform TSLP under basal conditions. When the skin barrier is intact, this difference may be negligible. But when a barrier defect (such as a filaggrin mutation) floods the skin with allergen exposure, lower TSLP output fundamentally changes the amplitude of the resulting Th2 response — which is precisely what the gene-gene interaction data shows.

The Evidence

The clearest evidence comes from the Pediatric Eczema Elective Registry⁴⁴ Pediatric Eczema Elective Registry
A multicenter longitudinal registry of children with atopic dermatitis followed from early childhood into adolescence (PEER), where 796 children were followed prospectively. Among white children, the T allele at rs1898671 was significantly associated with less persistent atopic dermatitis (OR 1.72; 95% CI 1.11–2.66; P = .01). In children who also carried filaggrin (FLG) loss-of-function mutations — the strongest known genetic risk factor for AD — the TSLP T allele dramatically amplified the disease-moderating effect (OR 4.92; 95% CI 2.04–11.86). This gene-gene interaction makes mechanistic sense: FLG mutations create the skin breach that maximizes TSLP release; the rs1898671 T allele then limits how loudly the alarm sounds.

A 7.6-year follow-up study⁵⁵ 7.6-year follow-up study
842 children, ~6,396 person-years of observation of the same registry found that TT homozygotes for rs1898671 were substantially less likely to require topical calcineurin inhibitors — a second-line immunosuppressive class — for disease control (OR 0.16; 95% CI 0.06–0.42). When children did discontinue calcineurin inhibitors, T allele carriers were more likely to stop all treatments entirely (OR 0.45; 95% CI 0.26–0.76), consistent with genuine disease remission rather than treatment switching.

A fine-mapping study⁶⁶ fine-mapping study
A genetic technique that sequences all variants in a region at high resolution to identify which specific SNP drives the association signal, rather than which SNP happens to be genotyped on a chip using targeted massively parallel sequencing in two independent cohorts (741 + 585 children) confirmed the T allele's protective effect: white children with the variant were less likely to develop AD at all (OR 1.41; 95% CI 1.20–1.66), with heterozygotes showing stronger protection (OR 1.91) than homozygotes (OR 1.28) — a non-linear pattern that suggests haploinsufficiency or threshold effects in the TSLP signaling chain.

One important caveat: rs1898671 has divergent effects across atopic conditions. A meta-analysis of 6,351 rhinitis cases⁷⁷ meta-analysis of 6,351 rhinitis cases and 11,472 controls found the T allele associated with modestly increased allergic rhinitis risk (OR 1.13; 95% CI 1.07–1.20). This opposing direction is not contradictory — it likely reflects the different inflammatory contexts of upper airway vs. skin-barrier pathology and the TSLP isoform balance in different tissue compartments. For GeneOps users, this means the T allele's favorable effect on AD persistence does not imply lower risk of all atopic conditions.

Practical Implications

T allele carriers with atopic dermatitis can take some reassurance that their genetics favor a milder disease course and higher probability of remission. TT homozygotes in particular are markedly less likely to require systemic or intensive topical immunosuppression over time. This does not eliminate the need for standard AD management — emollients, barrier repair, and trigger avoidance remain essential regardless of genotype — but it informs expectations about long-term trajectory.

For CC homozygotes (no T allele), the data suggest higher TSLP activity and a greater probability of persistent, treatment-requiring disease. Proactive barrier maintenance and early dermatologist involvement at first signs of significant flares may matter more for this group. Additionally, if they also carry FLG loss-of-function mutations (testable separately), the combination identifies the highest-risk AD subgroup. Anti-TSLP biologics (tezepelumab, in trials for AD) are a treatment avenue particularly relevant for high-TSLP individuals who fail standard therapy.

Interactions

The interaction between rs1898671 and filaggrin (FLG) loss-of-function mutations is the most clinically documented at this locus. In individuals with both a FLG null allele and the TSLP rs1898671 T variant, disease persistence was markedly reduced compared to those carrying FLG mutations without the T allele (OR 4.92). This suggests the two genes operate in sequence: FLG determines how much allergen penetrates; TSLP determines how loudly the alarm sounds in response. Reducing either signal attenuates the cascade.

The 5q22.1 locus (TSLP neighborhood) also harbors rs1837253 in TSLP's upstream region, a variant more strongly associated with asthma and eosinophilic esophagitis; rs1898671 and rs1837253 tag partially overlapping but distinct TSLP regulatory signals.

TSLP is upstream of the IL-4Rα signaling axis targeted by dupilumab. In AD patients who fail to respond adequately to dupilumab, elevated TSLP-driven IL-33 and TSLP-independent ILC2 activation may partially explain residual disease — making TSLP genotype relevant to treatment selection discussions.