Granulomatous abscess of the ulnar nerve in a case of paucibacillary leprosy given multidrug therapy.

Although leprosy is a granulomatous disease that is potentially treatable with the multidrug therapy (MDT) currently recommended by the World Health Organization (WHO), a few ‘borderline tuberculoid’ cases harbour Mycobacterium leprae in their nerves for many years after they have received such treatment and become clinically inactive (Chaudhuri et al., 1998). Pure neuritic leprosy is most frequently found in India and Nepal, where it accounts for 5%–10% of all leprosy patients (Britton and Lockwood, 2004). Although, in such disease, the fusiform swelling of the ulnar nerve is a classic finding, abscesses involving a nerve also sometimes occur, albeit rarely (Sehgal, 1966). Such abscesses that are detected tend to develop in the major nerve trunks, most frequently in the ulnar nerve (Salafia and Chauhan, 1996). Histological examination is the ‘gold standard’ for diagnosis of such abscesses, as the presence of neural inflammation differentiates leprosy from other granulomatous disorders (Britton and Lockwood, 2004), but fine-needle aspiration cytology (FNAC) can also be useful (Siddaraju et al., 2009). Imaging, by ultrasonography and/or magnetic resonance, is generally unhelpful, as the features of neural leprosy can also be found in hypertrophic neuropathy, amyloid infiltration and chronic relapsing neuropathy, but the detection of a nerve granuloma or abscess is often indicative of leprosy (Hari et al., 2007).