Hansen’s Disease with Pure Nerve Involvement and Perineural Abscess Mistaken for Peripheral Nerve Sheath Tumour

Nerve abscess is an infrequently reported complication of leprosy. It is also an uncommon first manifestation of leprosy. In this case, due to the absence of classic signs and symptoms, such as skin lesions, hypoesthesia, and loss of sensation, the swelling was clinically diagnosed as a peripheral nerve sheath tumour on initial presentation. The authors have described an unusual presentation of pure neuritic leprosy that showcased nerve abscess. Clinical presentation was swelling over the medial aspect of the right arm and ulnar aspect of the right forearm, and clawing of the fourth and fifth digits of the right hand, with no signs of inflammation present on the skin surrounding the swelling. Hansen’s disease with pure nerve involvement could not be considered as a differential diagnosis solely based on clinical examination, therefore posing a diagnostic challenge. On ultrasonography, the right ulnar nerve showed diffuse intermittent thickening and a heterogeneously hypoechoic fusiform area with internal echoes at the site of swelling indicating a nerve abscess. These led the authors to the diagnosis of leprosy with perineuronal abscess. Histopathology confirmed the diagnosis by revealing granulomas and acid-fast Hansen’s bacilli. The patient showed dramatic response to surgery, multidrug therapy, and systemic corticosteroids.