Thickening of peripheral nerves in neurofibromatosis

Introduction

Thickening of peripheral nerve trunk is one of the cardinal features of leprosy. Localised tumours arising from sheaths of peripheral nerves causing nerve thickening can sometimes be seen in neurofibromatosis. We report a case of neurofibromatosis with gross enlargement of all peripheral nerve trunks simulating leprosy.

Case Report

A 14-year-old male patient presented to skin OPD with history of multiple asymptomatic swellings all over body of 3 years duration. On cutaneous examination the findings were unmistakable for neurofibromatosis [Figure - 1]. Other systems were clinically normal. Interestingly, some of the nerves including great auricular [Figure - 2] and a cutaneous nerve twig in forearm appeared prominent. On palpation all the peripheral nerve trunks (great auricular, ulnar, common peroneal and posterior tibial) revealed uniform bilateral symmetrical thickening, they were non tender. No sensory or motor deficit was demonstrated. Routine investigations were normal. A biopsy of radial cutaneous nerve showed histologic changes consistent with neurofibromatosis.

Discussion

Neurofibromatosis (NF) is one of the neuro-cutaneous disorders characterised by pigmented macules (cafe-au-lait spots), tumours of skin and nervous system. A majority of cases are inherited (autosomal dominant).[4] The central nervous tumours occurring in neurofibromatosis have received much attention. The same, however, can not be said about peirpheral nerve tumours. In tropics, leprosy is by far the commonest cause of peripheral nerve thickening. Literature also mentions some other rare causes of peripheral nerve thickening such as pachydemoperiostosis, primary amyloidosis, familial hypertrophic interstitial neuritis, recurrent or chronic progressive polyneuritis.[1]

Generalised nerve thickening is only sporadically reported in neurofibromatosis.[2] When encountered, such nerve thickening can easily be mistakened for generalised nerve thickening of leprosy. Moreover, there have been case reports where both these diseases coexist[3] which would make it still more difficult to pin point the cause of peripheral nerve thickening. In our patient because the cutaneous findings were unequivocal for NF, leprosy was not considered in differential diagnosis. However, in patients where there are no cutaneous lesions of NF, the issue can not be resolved without a nerve biopsy. We therefore recommend that neurofibromatosis should be remembered as a cause of generalised nerve thickening lest it should create confusion with leprosy.