T-Cell–Driven Fibroinflammation Inducing Follicular Dedifferentiation in Alopecia Areata and IgG4-Modified Disease

The definition of IgG4-related diseases incorporates a broad range of systemic diseases particularly a subset dominated by fibroinflammation. CD4+cytotoxic T cells have emerged as the major driving force for the fibroinflammation, and the pathogenetic role of IgG4 still remains to be determined. Cutaneous involvement is uncommon and is not well defined as elevated tissue IgG4 plasma cells are not a specific marker and prominent cutaneous fibroinflammation is often absent in cutaneous disease. We report the case of a patient with longstanding alopecia universalis and severe atopic dermatitis who presented with diffuse induration and mottled dyspigmentation of his scalp. Multiple scalp biopsies revealed diffuse interfollicular fibroinflammation and IgG4 plasma cells with induction of distinctive dedifferentiated follicles not seen in alopecia areata. This complex case may provide insight into the role of specific subsets of T cells not only in respect to the fibroinflammation linked to IgG4-related diseases but also the capacity to modify disease, follicular stem cell activation, immune privilege, cytotoxicity in alopecia areata, and the presence of atopy that may have contributed to the pathogenesis of this case.