Pure neuritic leprosy: Resolving diagnostic issues in acid fast bacilli (AFB)-negative nerve biopsies: A single centre experience from South India

Abstract

Background and Purpose:Demonstration of lepra bacilli is essential for definite or unequivocal diagnosis of pure neuritic leprosy (PNL) on nerve biopsy. However, nerves always do not show bacilli owing to the changes of previous therapy or due to low bacillary load in tuberculoid forms. In absence of granuloma or lepra bacilli, other morphologic changes in endoneurium and perineurium can be of help in making a probable diagnosis of PNL and treating the patient with multidrug therapy.Materials and Methods:Forty-six biopsies of PNL were retrospectively reviewed and histologic findings were compared with 25 biopsies of non leprosy neuropathies (NLN) including vasculitic neuropathy and chronic inflammatory demyelinating polyneuropathy (CIDP). The distribution of endoneurial infiltrate and fibrosis, perineurial thickening, and myelin abnormalities were compared between PNL and NLN biopsies and analyzed by Chi-square test.Results:Out of 46 PNL casses, 24 (52.17 %) biopsies were negative for acid fast bacilli (AFB). In these cases, the features which favor a diagnosis of AFB-negative PNL were endoneurial infiltrate (51.1%), endoneurial fibrosis (54.2%), perineurial thickening (70.8%), and reduced number of myelinated nerve fibers (75%).Interpretation and Conclusion:Nerve biopsy is an efficient tool to diagnose PNL and differentiate it from other causes of NLN. In absence of AFB, the diagnosis of PNL is challenging. In this article, we have satisfactorily evaluated the various hisopthological features and found that endoneurial inflammation, dense fibrosis, and reduction in the number of myelinated nerve fibers are strong supportive indicators of PNL regardless of AFB positivity.

Hansen's Neuritis Revisited – A Clinicopathological Study

“…Among 46 cases of PNL, peripheral nerves were thickened in 32.6% cases, followed my trophic ulcers in 21.7% cases, muscle wasting, claw hand, and foot drop in 15.2%, 10.8%, and 8.7% cases, respectively. [ 13 ] Mononeuritis multiplex was the most frequent clinical and electrophysiological pattern of nerve dysfunction, with sensory (89% of all cases) more than motor (81%) dysfunction and predominant axonal neuropathy[ 14 ] comparable to the current study. Bilateral facial palsy is less common than unilateral facial palsy and the incidence of the same in leprosy varies from 3% to 24.59%.…”

“…Another study reported epithelioid granulomas in 14% cases. [ 13 ] Reduction in myelinated fibres was noted in 55.6% cases,[ 16 ] unlike moderate-to-complete degree of myelinated fiber loss in all the cases in this study. Loss of myelinated fiber and Schwann cells is consistent with decrease in immunohistochemical staining of neurofilament in 100% HN biopsies, nerve growth factor receptor loss in 81.8%, PGP 9.5 staining loss in 100%, and loss of S-100 as well as myelin basic protein immunoreactivity in 90.9% cases each.…”

“…in 46 cases of PNL, there were 47.8% cases of BT, followed by 23.9%, 13%, and 10.8% cases of BL, TT, and BB, respectively. [ 13 ] Endoneurial, perineurial, and epineurial inflammation was seen in 39.8%, 39.8%, and 27.7% cases, respectively. Epithelioid granulomas were described in 13.2% cases.…”

“…[ 18 ] Caseous necrosis was recorded in one case of TT (case-15; present study) as was reported by Hui et al . [ 13 ]…”

“…[ 17 ] In the present study, lepra bacilli were highlighted by Fite-Faraco stain in 44.4% cases, comparable to 47.8% in the study by Hui et al . [ 13 ] Other ancillary tests were not done for the cases reviewed in our study.…”