Role of nerve biopsy PCR for M leprae in the diagnosis of pure neuritic leprosy – a cross sectional study

Background

Peripheral nerves are the main organs affected by leprosy. Nerve involvement starts early in the disease and can frequently be the only symptom. Because of the over-reliance on clinical competence and the lack of an easy-to-use yet trustworthy diagnostic instrument, the diagnosis of pure neural leprosy (PNL) has remained subjective. The identification of PNL requires the demonstration of lepra bacilli through nerve biopsy. Nonetheless, nerves do not always exhibit bacilli because of altered prior treatment or low bacillary load. The probable diagnosis of PNL may be aided by additional morphologic changes in the endoneurium and perineurium in the absence of granuloma or lepra bacilli. Nerve biopsy PCR could be more accurate in the definitive diagnosis of PNL.

Aim

To have an objective diagnosis of PNL, to assess the diagnostic value of nerve biopsy PCR, and to correlate with neural histopathology in PNL.

Material and method

Clinically diagnosed PNL patients attending a tertiary care center in Maharashtra from 2021–2024 were subjected to nerve biopsy histopathology (HPE), nerve biopsy PCR, and nerve conduction study (NCS), and followed up with reports.

Results

55 patients were clinically diagnosed as PNL, out of which 4 denied consent and 5 were lost to follow-up with investigation. Out of 46 patients, 30 (65%) underwent ulnar cutaneous nerve biopsy, and 16 (35%) underwent sural nerve biopsy. Histopathology showed features definitive for leprosy in 11 (23.9%), probable in 10 (21.7%), and normal in 25 (54.3%). Only 2 (4.3%) were positive, and 44 (95.7%) were negative for AFB by Fite-Faraco stain. Nerve biopsy PCR was positive in 30 (65.2%). NCS showed sensory involvement in 12 (26.1%), 6 (13%) had motor involvement, 17 (36.9%) had both motor and sensory involvement, and 11 (23.9%) had normal findings.

Conclusions

The accuracy of nerve biopsy PCR is higher than histopathology in confirming the diagnosis of PNL.