A Case of Fluoroscopy‐Induced Subacute Radiation Dermatitis Histologically Mimicking Sclerodermiform Lupus: Immunohistochemical Analysis of Cytotoxic Memory T‐Cell Markers

The histological hallmark of fluoroscopy-induced subacute radiation dermatitis (FISARD) is basovacuolar interface reaction with satellite cell necrosis mediated by CD8+ cytotoxic T-cells. Most published cases are described in patients who had a single interventional exposure. Here we report a case of FISARD in a 78-year-old man who underwent two cardiovascular interventions within 2 months. Biopsy of the skin lesion on his left back revealed not only epidermal cytotoxic interface activity with superficial perivascular dermatitis but also deep perivascular and interstitial dermal lymphoid infiltrates and dermal sclerosis, features overlapping with lupus and inflammatory morphea. Immunohistochemistry revealed intraepidermal and dermal expression of CD3, CD8, TIA-1, and CD45RA, likely corresponding to terminally differentiated effector memory cytotoxic T cells (TEMRA). In contrast, expression of CD57, a marker of late memory T-cells implicated in scleroderma pathogenesis, was absent in the epidermis but present in the dermis. This case adds to the spectrum of histopathologic findings of FISARD possibly related to the cumulative radiation injury from multiple fluoroscopic procedures. Given the increasing use of fluoroscopy, recognition of this histopathological pattern could aid in the timely and accurate diagnosis of this condition. A potential role of memory CD8+ T-cells in disease pathogenesis is discussed.