aGVHD in an ICI-treated patient with mixed chimera. (A) Photographs of an ICI-treated patient with mixed chimera after alloBMT who developed erythematous maculopapular skin lesions. (B) Skin sampling revealed lymphocytic exocytosis and scattered intraepidermal dyskeratotic cells, overlying a scant dermal perivascular inflammatory infiltrate composed of lymphocytes and histiocytes with vacuolar interface dermatitis including vacuolar changes of basal keratinocytes. (C) Immunohistochemistry using an anti-CD3 antibody showed T-cell infiltrate involving the epidermis and superficial dermis.