Morphea skin carried expanded macrophage subsets and an interferon signature

Design

single-cell RNA sequencing with spatial transcriptomics and ligand-receptor interaction analysis

Population

untreated lesional skin from patients with localised scleroderma, compared with healthy skin

Primary outcome

immune cell composition and intercellular signalling in lesional skin

Effect

T follicular helper-like cells more prevalent; TREM2+ and FCN1+ macrophages and LAMP3+ dendritic cells expanded with an interferon signature; increased T/NK to myeloid signalling via CXCL, CCL, TNF and type II interferon

Localised scleroderma is treated with methotrexate and corticosteroids largely because they work, not because the target is known. This study applied single-cell RNA sequencing to untreated lesional skin, with spatial transcriptomics and ligand-receptor analysis to locate the altered populations, and identified 17 main cell types.

The T and NK compartments were unremarkable in proportion, with one exception: T follicular helper-like cells were more prevalent in lesional than healthy skin. The myeloid compartment was where the differences sat. TREM2-positive and FCN1-positive macrophages and LAMP3-positive dendritic cells were all expanded, and all carried an interferon signature. Ligand-receptor analysis showed increased signalling between the T/NK and myeloid compartments, running through CXCL, CCL, TNF and type II interferon pathways.

This is descriptive immunology with no outcome data, and it does not change what anyone prescribes this week. Its value is in naming candidate targets in a disease where the treatment options have been unchanged for two decades, and in pointing at the interferon axis - which matters because JAK inhibitors, already used in other interferon-driven skin disease, would be the obvious thing to test. That is a trial to want, not a prescription to write.

• Continue current management - methotrexate with or without systemic corticosteroid for active, extensive or functionally threatening morphea
• Do not extrapolate to off-label JAK inhibitor use; this identifies a pathway, not a treatment
• Note the samples were from untreated skin, so the signature describes active disease rather than treatment effect
• Keep assessing activity clinically - erythema, violaceous border, lesional warmth - since no biomarker follows from this
• Watch for trials of interferon or JAK-directed therapy in localised scleroderma

Why it matters

It gives a disease treated by convention a mechanism that could be tested directly.

Don't overread it

Descriptive single-cell profiling without outcome data - identifying a pathway is not evidence that blocking it helps.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.