Posterior interosseus nerve palsy resulting from inflammatory myofibroblastic pseudotumor: case presentation

Local compression by a mass lesion is a potential cause of posterior interosseous nerve (PIN) palsy. Reported cases of PIN pathology do not include inflammatory myofibroblastic pseudotumor. We report the case of a 44-year-old woman with a 3-month history of progressive weakness of the left finger extensors. Sonographic imaging identified a mass compressing the PIN, and histologic examination of the specimen revealed an inflammatory myofibroblastic pseudotumor. Complete resection of the mass while sparing the nerve was possible, and the patient has regained functional use of the left hand. The differential diagnosis of PIN palsy should include inflammatory myofibroblastic pseudotumor.