LAUSR

Objectives Leprosy a chronic granulomatous infection of skin and nerves caused by Mycobacterium leprae manifests with hypopigmented and hypoesthetic patches. The aim of our study was to evaluate small fibres dysfunction, by means of laser evoked potentials (LEPs), in these hypoesthetic lesions. Methods A 55-year-old woman, natural from Bolivia, was referred for a suspected tuberculoid leprosy(TL). The patient presented a right thickened superficial radial nerve, infiltrated erythematous and hypochromic patches, some ring-shaped, predominantly in the trunk and upper limbs, with well-defined borders and hypoesthetic. Results Electrophysiological studies evidenced reduced sensory nerve action potential amplitude of the right thickened superficial radial nerve compared to the non-thickened contralateral one. LEPs evidenced reduced amplitude or absent responses stimulating skin dyspigmented patches and normal evoked potentials in the surrounding areas. Skin biopsy showed inflammatory granulomatous infiltration of superficial and deep dermis and enlarged nerve funicles with well formed non caseating granulomas, few epithelioid histiocytes and Langhans-type multinucleated giant cells. Acid-fast bacilli were not observed. Discussion In leprosy, small fibres are most vulnerable for infection with lepra bacilli. LEPs constitute a useful tool to explore small fibre neuropathy of hypoesthetic patches in leprous patients and can objectify and quantify this sensory impairment. Conclusions LEPs abnormalities suggest Adelta fibre involvement in the area of an overlying hypoesthetic lesion and preserved Adelta fibre function in the surrounding areas. Significance This is the first report that documents the use of LEPs as a reliable method to objectify small nerve function impairment.