Sensory mononeuritis: differentiating pure neural leprosy from non-systemic vasculitic neuropathy

We describe two cases of sensory mononeuritis that presented with similar past medical histories, and clinical and electrophysiological features. The two patients were females who had resided in areas endemic for leprosy (Brazil). Both developed a progressive, purely sensory, painful mononeuritis distally in the lower limbs with sensory nerve potentials asymmetrically reduced in amplitude. The sural nerve biopsy performed in Patient 1 showed granulomatous inflammation of the epineurial tissue, consistent with paucibacillary pure neural leprosy (PNL) while in Patient 2 there were signs of vascular inflammation consistent with non-systemic vasculitic neuropathy (NSVN). Patients 1 and 2 both improved following targeted treatment with rifampicin and dapsone vs. rituximab, respectively.