An Attempt to Improve Pure Neural Leprosy Diagnosis Using Immunohistochemistry Tests in Peripheral Nerve Biopsy Specimens

The diagnosis of pure neural leprosy (PNL) is based on clinical and laboratory data, including the histopathology of nerve biopsy specimens and detection of Mycobacterium leprae DNA by polymerase chain reaction (PCR). Given that histopathologic examination and PCR methods may not be sufficient to confirm the diagnosis, immunolabeling of lipoarabinomanan (LAM) and/or phenolic glycolipid 1 (PGL-1) M. leprae wall components was utilized in the present investigation in an attempt to detect any vestigial presence of M. leprae in acid-fast bacilli (AFB)(-) nerve samples. Twenty-three PNL nerve samples (6 AFB(+) and 17 AFB(-)PCR(+)) were cryosectioned and subjected to LAM and PGL-1 immunohistochemical staining by immunoperoxidase. Five nonleprosy nerve samples were used as controls. The 6 AFB(+) samples showed LAM/PGL-1 immunoreactivity. Among the 17 AFB(-) samples, 8 revealed LAM and/or PGL-1 immunoreactivity. In 17 AFB(-)PCR(+) patients, just 7 yielded LAM(+) and/or PGL-1(+) nerve results. In the PNL cases, the detection of immunolabeled LAM and PGL-1 in the nerve samples would have contributed to an enhanced diagnostic efficiency in the absence of molecular diagnostic facilities.