Track

Abstract

Lipophagic panniculitis is an autoimmune panniculitis pathogenetically linked with a type IV immune response targeting adipocytes. The subsequent adipocyte injury results in a massive influx of scavenger macrophages which imbibe released lipid from damaged adipocytes. Lupus profundus is another autoimmune lymphocyte-mediated panniculitis which can progress to a form of panniculitic T-cell lymphoma. We report a 50-year-old woman who presented initially two years ago with classic clinical and light microscopic findings of autoimmune lipophagic panniculitis. Although initially responding to plaquenil, she developed a worsening of her panniculitis. A new biopsy showed an extensive atypical lymphocytic and histiocytic lobular panniculitis with foci of subcutaneous leukocyte necrosis associated with microvascular thrombosis and frank colonization of adipocytes by lymphocytes. Immunophenotyping demonstrated a predominance of CD4⁺ αβ T cells with marked loss of CD5, partial loss of CD7, and aberrant expression of cytotoxic proteins (TIA-1, granzyme). The findings were compatible with subcutaneous atypical cytotoxic CD4⁺ panniculitic T-cell dyscrasia. Due to the lack of greater lymphoid atypia it was not considered diagnostic of lymphoma. The unique phenotype in this case reflects clonal expansion of immunosenescent CD4⁺ cytotoxic T cells driven by chronic antigenic stimulation in the setting of autoimmunity. This atypical panniculitis could presage an immunosenescent cytotoxic CD4⁺ panniculitic T-cell lymphoma drawing a parallel between atypical lymphocytic lobular panniculitis and lupus profundus as panniculitic T-cell dyscrasis that can eventuate into subcutaneous T-cell lymphoma.