An unusual cause of mononeuritis multiplex

A middle-aged man of South Asian decent presented with a 4-month history of bilateral sensory disturbance affecting the median nerve distribution and dorsum of both feet. Neurological examination was otherwise normal. A patchy absence of sensory responses was noted on nerve conduction studies and electromyogram (NCS/EMG). Over the next 3 months sensory symptoms progressed to involve median, radial, ulnar, sural and peroneal nerves bilaterally. Repeat NCS/EMG confirmed a mononeuritis multiplex predominantly involving the sensory fascicles. Areas of hypopigmentation, a right-lower motor facial weakness and ophthalmic branch trigeminal nerve involvement were noted on examination. Punch skin biopsy as well as sural nerve biopsy demonstrated chronic granulomatous inflammation without evidence of Mycobacterium. A slit skin smear test demonstrated Mycobacterium leprae consistent with a diagnosis of primary neuritic leprosy. In the appropriate clinical context, leprosy should be included in the differential diagnosis of mononeuritis multiplex.