Nerve abscess in pure neural leprosy mistaken for peripheral nerve sheath tumour with disastrous consequence: what can we learn?

A 34-year-old Indian man presented to an orthopaedician with gradually progressive hypoesthesia affecting his right lower limb and an ipsilateral common peroneal nerve swelling around the knee. The nerve swelling was diagnosed as a peripheral nerve sheath tumour based on MRI findings and was excised, only to be revealed as leprous nerve abscess on histopathology later. The patient developed right foot drop as a result of common peroneal nerve biopsy. This case presents several learning points in the diagnosis of pure neural leprosy.