Estudo das alterações morfológicas na neuropatia da hanseníase: aplicações práticas no diagnóstico e implicações sobre a patogenia da doença

Abstract

Early diagnosis is an important strategy to prevent transmission and physical disability of patients with this disease. The search for histopathological alterations in the cutaneous nerve branches gains importance in the search for evidence of leprosy etiology, when the Mycobacterium leprae is not detected in the samples. The present study was divided into three fronts (A, B and C): Study A: morphological study of cutaneous nerve branches and appendages in cutaneous lesions suspected of leprosy. The groups were divided according to the histological diagnosis issued by pathologists, being divided into: HANSEN group, INCONCLUSIVE group (INC) and the group of OTHER DISEASES not related to leprosy (OD).Morphological indices of nerve damage calculated by the ratio between the number of nerve branches with a given alteration and the total number of nerves in the sample were elaborated. The HANSEN group, compared to the INC and OD samples, demonstrated, significantly higher indexes of nerve alterations (perineural hyperplasia, endoneurial infiltrate perineurial infiltrate, near but without contact with the nerve branch infiltrate and increased endoneurial cellularity). The frequency of inflammatory infiltrate involving the appendages was also higher in the HANSEN group. In regard to the quantification of anti-PGP 9.5 immunoreactive nerve fibers (protein 9.5 gene product), the HANSEN group had the lowest immunoreactivity index in the nerve branches as well as in the surroundings of the skin appendages compared to the INC and OD groups. Study B performed histopathological and ultrastructural examination of the innervation in hypoesthetic skin with normal visual appearance obtained from patients with the pure neural form of the disease. There was partial agreement between the findings in the nerve trunk and in the cutaneous branches examined; this was represented by increased matrix in 3 cases, endoneurial cellularity in 2 and perineurial thickening in 4. Out of 11 cases, 7 presented denervated Schwann cells and 5 nerves showed the presence of collagen pockets. Study C determined the quantification of non-myelinated fibers in peripheral nerve trunk of patients with pure neural form compared to a group of nerve samples from patients with other etiologies unrelated to leprosy. There was no significant difference in the comparison. Study A did not discriminate more cases of leprosy in the group where the diagnosis was inconclusive but showed that the highest mean indexes of nerve and of attachment skin appendages belonged to the HANSEN group. Likewise, the marking of nerve fibers by PGP 9.5 showed the greatest reduction, found in the HANSEN group. Study B showed that ultrastructural examination of skin biopsy may reveal changes not noticeable by conventional optical microscopy, suggesting that the skin ultrastructural analysis may be helpful in the histopathological diagnosis of leprosy. Study C showed no significant difference in the quantity of nonmyelinated fibers between the pure neural leprosy and nonleprosy groups.