Leopard skin appearance of cutaneous polyarteritis nodosa on18Ffluorodeoxyglucose positron emission tomography

An 8-year-old girl was referred to us with fever, erythematous papules and painful subcutaneous nodules located over her extremities and bilateral arthritis of the ankles and knees. Laboratory findings revealed leucocytosis (13 410/mm3) and elevated CRP concentration (1.4 mg/dl) and ESR (61 mm/h). MRI of the thighs revealed multiple high-signal nodular lesions throughout the subcutaneous tissue and subfascial muscle tissue of the thighs. 18F-Fluorodeoxyglucose PET (18F-FDG-PET) revealed a unique, leopard skin appearance with multiple, disseminated hot spots throughout the muscle and subcutaneous tissue in upper and lower extremities (Fig. 1). A skin biopsy of a subcutaneous nodule revealed necrotizing vasculitis. The diagnosis of cutaneous PAN was made. She was treated with prednisolone and maintained on ciclosporin and monthly infusions of CYC. 18F-FDG-PET is a promising new technique to evaluate metabolic activity, with 18F-FDG accumulations in cells that have a high rate of glycolysis [1]. Increased uptake of 18F-FDG is observed in vasculitis lesions with infiltrations of inflammatory cells [2]. In this patient, 18F-FDG-PET revealed a unique, leopard skin appearance with multiple, disseminated hot spots throughout the muscle and subcutaneous tissue. These findings indicate that 18F-FDG-PET is useful for the evaluation of the extent and location of inflammation in patients with cutaneous PAN.