Unmasking Iododerma: A Distinctive Histopathologic Pattern of Neutrophil-Rich Dermatosis With Haloed Cryptococcoid Bodies in the Setting of Hydralazine Exposure and Autoimmune Serologic Abnormalities.

Cutaneous iododerma is a rare adverse reaction to iodine-containing compounds that may clinically and histopathologically mimic infection, vasculitis, malignancy, and other neutrophilic dermatoses. Although most commonly associated with iodinated contrast exposure, a variety of predisposing factors and potential associations have been reported, including impaired renal function, repeated iodine exposure, and more recently, hydralazine therapy in isolated cases. We report two women with chronic kidney disease and recent iodinated contrast exposure who developed rapidly progressive, painful, bullous, erosive, and retiform eruptions after contrast administration. Both patients had concurrent hydralazine exposure. Initial clinical considerations included deep fungal infection, ecthyma, Sweet syndrome, drug eruption, and vasculitis. Histopathologic examination demonstrated a neutrophil-rich dermal infiltrate with numerous basophilic haloed cryptococcoid bodies and vasculitis with fibrinoid necrosis. Fungal, bacterial, and acid-fast stains were negative, and extensive infectious evaluations were unrevealing. Markedly elevated serum and urine iodine levels supported the diagnosis of iododerma. Both patients exhibited multiple immunologic abnormalities, including positivity or elevated levels of p-ANCA and antinuclear, anti-histone, anti-myeloperoxidase, and anti-proteinase 3 antibodies. These findings were interpreted cautiously given concurrent hydralazine exposure, the absence of definitive systemic autoimmune vasculitis, and the potential for reactive serologic abnormalities in the setting of intense neutrophilic inflammation. Both patients improved following corticosteroid therapy, iodine clearance, and discontinuation of hydralazine. These cases emphasize the diagnostic importance of recognizing haloed cryptococcoid bodies within a neutrophil-rich infiltrate associated with vasculitic injury as part of the histopathologic spectrum of iododerma. The significance of hydralazine exposure in the pathogenesis of iododerma remains uncertain and warrants further investigation.