Bilateral medial fingernail dystrophy as a presenting feature in a patient with leprosy

An 18 year old male student presented at the dermatology clinic complaining of discolouration, thickening, grooving and deformation of the medial three fingernails of both hands for the last 4 months. He was not involved in any manual work and denied that he bit his nails. There was no history of any major medical or surgical events in his recent past. Examination of the nails revealed opaque leukonychia of the distal nail plates of the fourth and fifth digits bilaterally. The affected nails also showed horizontally transverse grooves, blackish discolouration and roughness with a flattening of their normal contour. The right third fingernail was also affected similarly with a horizontal groove near the distal edge with discolouration of the nail plate. The left third fingernail showed less prominent changes, yet a partial horizontal groove was visible near the proximal end (Figure 1). A nail clipping immersed in 10% potassium hydroxide and fungal culture did not reveal any fungal elements. Blood sugar and X-ray of the hands were normal. This distribution of nail changes approximately matched the ulnar nerve distribution. Both ulnar nerves were found to be thickened on palpation while other peripheral nerve trunks were not enlarged. Bearing in mind the possibility of leprosy, diagnostic signs were