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Mast cells (MCs) are tissue-resident cells with various immunologic functions. MCs are increased in atopic dermatitis (AD) skin and can contribute to the inflammation. Although skin MCs are inducible from bone marrow (BM) cells in vitro, they are maintained locally by self-proliferation in the steady state in vivo. However, how skin MCs are increased in AD skin, including the infiltration of BM-derived MC progenitors (MCps) and their differentiation, remains unclear.We sought to identify and characterize BM-derived MCps in AD skin.BM-derived MCps in AD skin were analyzed by flow cytometry using BM-chimeric mice and parabiosis in an MC903-induced AD model. BM-derived MCps in AD-like skin were compared with resident MCs for gene expression by RNA- sequencing analysis.We observed local proliferation of resident MCs and an increase in BM-derived MCs in AD-like skin. BM-derived MCs in the skin were derived from circulating MCps and were distinguishable from resident MCs by integrinβ7. RNA- sequence analysis showed that integrinβ7BM-derived integrinβ7