A case of polyarteritis nodosa limited to lower legs with a high titer of MPO-ANCA under precedence of idiopathic pulmonary fibrosis

A 58-year-old man with a 15-year history of idiopathic pulmonary fibrosis was hospitalized for rapid progression of muscle weakness to bilateral foot drop. Although laboratory data revealed high titers of myeloperoxidase anti-neutrophil cytoplasmic antibody (489 EU), the patient was diagnosed as polyarteritis nodosa limited to the lower portions of the legs. Despite of the treatment with large doses of corticosteroids and cyclosporin A, his symptoms barely improved during the following two months.