Churg‐Strauss syndrome presenting as scar reactivation: histopathologic features and an illustration of ‘locus minoris resistentiae’

We report a 33‐year‐old female with cutaneous involvement by Churg‐Strauss syndrome confined to surgical scars that were obtained 13 years before. She presented to the emergency department with 2‐day history of fever, night sweats, right‐sided weakness, hoarseness and worsening asthma symptoms. She was found to have an eosinophilia and two sub‐5‐mm pulmonary nodules. The patient also reported that the scars on her right thumb, inner wrist and back had been swollen, red and painful for 2 days. Examination revealed tender, erythematous, well‐healed edematous scars studded with small skin colored papules. She had no clinical findings that were classic for cutaneous vasculitis. A skin biopsy of a scar revealed perivascular and palisading granulomatous inflammation consisting of histiocytes and neutrophils with leukocytoclasia. Focal vascular injury was identified. Scattered tissue eosinophils were seen. Special stains were negative for infection. Thereafter, she was started on intravenous steroids, at which point the fever, pulmonary and cutaneous symptoms subsided. Although scar sarcoidosis is a well‐described phenomenon, granulomatous inflammation and vasculitis seen in Churg‐Strauss syndrome exclusively manifesting in well‐healed surgical scars highlights the unique features seen in this case and draws attention to the concept of locus minoris resistentiae. This case also highlights how a skin biopsy in the setting of suspected systemic vasculitis can confirm the presence of vasculitis and/or granulomatous inflammation and obviate the need for more invasive, higher risk procedures such as lung biopsy.