A case report on imaging findings of rare segmental necrotizing granulomatous neuritis of leprosy involving ulnar nerve.

Introduction: Segmental necrotizing granulomatous neuritis (SNGN) is a rare complication of leprosy involving peripheral nerves. It can appear alone in cases of pure neuritic leprosy or in combination with cutaneous lesions.

Case presentation: A 15-year-old female diagnosed with borderline tuberculoid leprosy who received prior multidrug therapy presented 2 years later with occasional pain and tingling sensations along the inner aspect of her right arm and forearm. Imaging findings suggested SNGN, which was corroborated by cytopathological examination. She was considered relapsed from leprosy, and multi-drug therapy and steroids were started, following which she reported a decrease in the size of the swelling along with no further deterioration of the sensorineural deficit.

Discussion: SNGN, which is one of the rare complications of leprosy, can create diagnostic dilemmas as its differential diagnoses include reversal reactions, and peripheral nerve tumors (such as schwannoma and neurofibroma), which have been outlined in this article. SNGN is more likely when magnetic resonance imaging (MRI) shows a well-defined ovoid lesion with central necrosis and peripheral rim enhancement.

Conclusion: The incidence of SNGN is on the rise due to multi-drug therapy. In our case, the patient developed SNGN, which was considered a relapse from leprosy, and multi-drug therapy and steroids were started, following which the patient reported a significant reduction in the size of the swelling with no further deterioration of the sensorineural deficit. Hence, an appropriate diagnosis of SNGN through ultrasonography and MRI will lead to favorable outcomes, ultimately benefiting the patient.