Aspectos clínicos, moleculares, sorológicos e neurofisiológicos no diagnóstico precoce da neuropatia hansênica

Abstract

Introduction: The long incubation period of leprosy, its insidious symptoms and signs produce difficulties in its diagnosis and correct clinical classification. Early recognition of neural impairment in leprosy - especially in household contacts with subclinical infection and in the primary neural form, in which the classic laboratory and clinical findings of the disease are, by definition, absent - represents a great challenge in clinical practice. Objectives: This thesis was subdivided into two studies, whose objectives were to characterize the clinical, molecular, serological and neurophysiological aspects in the early diagnosis of leprosy neuropathy, in patients with suspected primary neural leprosy (PNL) and household contacts with subclinical infection. Methodology: In the first study, 70 patients with a diagnosis of PNL were recruited and, in the second study, 175 seropositive household contacts (SPHHC), defined as a subclinical infection, and one control group of 35 seronegative household contacts (SNHHC), accompanied in a national leprosy reference center of Brazil, in the period from 2014 to 2016. All the individuals were submitted to a clinical, laboratory and neurophysiological evaluation. A detailed methodological description and specific statistical analysis are provided separately in each study. Results: In Study 1, 61.4% (43/70) of the patients were clearly symptomatic, a group that all presented an asymmetrical peripheral impairment, predominantly sensorial. The presence of neural thickening was observed in 58.6% (41/70). Electroneuromyographic evaluation evidenced the presence of mononeuropathy in 51.4% (36/70); 52.9% (37/70) presented positivity by the anti-PGLl ELISA test and 78.6% (55/70) in M. leprae DNA detection by real time PCR (qPCR) in intradermic smear. The patients with a pattern of multiple mononeuropathy showed lower indices of anti-PGL-1 ELISA (p=0.0006), and higher frequencies of neural thickening (p=0.0008) and sensorial symptoms (p=0.01), when compared to the mononeuropathy group. The qPCR of nerve biopsies was positive in 60.8% (17/28). In Study 2, the qPCR analysis in peripheral blood was positive in 40.6% (71/175) of SPHHC versus only 8.6% (3/35) of SNHHC (p=0.0003). Intradermic smear evaluation found 4% (7/175) of SPHC with positive bacilloscopy while 47.4% (83/175) presented positivity in M leprae DNA detection by qPCR. In the SNHHC group, all presented negative bacilloscopy and only 17.1% (6/35) presented positive smear qPCR (p=0.0009). In electroneuromyographic evaluation, 31.4% (55/175) of SPHHC presented signs of neural impairment versus 13.3% (4/35) in the SNHHC group (p=0.0163). The presence of neural thickening conferred a 2.94- fold higher chance of ENMG alterations (OR, 2.94; p=0.0031). The SPHHC group presented a 4.04-fold higher chance of neural impairment (OR, 4.04; p=0.020). The peripheral blood qPCR positivity gives a 2.08-fold higher chance (OR, 2.08; p=0.028); and the presence of at least one BCG vaccine scar demonstrated 2.44-fold greater protection against neural impairment (OR, 0.41; p=0.044). Conclusion: In Study 1, the utilization of serological, molecular and neurophysiological tools in patients with suspicion of PNL contributed not only to early diagnosis, but also to a correct clinical classification and adequate treatment, thus preventing sequelae. Therefore, we propose a new recommendation for diagnosing PNL through the implementation of more specific and sensitive methods, aiming to make this condition less underdiagnosed. In Study 2, annual monitoring of domiciliary contacts through clinical exam and serological evaluation (anti-PGLl ELISA), for at least 5-7 years, demonstrated that seropositivity confers a greater chance of peripheral neural impairment evaluated by electroneuromyography and development of multibacillary forms. The combined use of three assays (ELISA anti-PGL1, peripheral blood qPCR and BCG scar) can identify individuals at high risk for developing leprosy neuropathy, not only indicating the early initiation of treatment in those whose diagnosis is confirmed by M. leprae DNA detection in qPCR of intradermic smear and/or altered ENMG, but also justifying chemoprophylaxis in those that do not yet present clinical or neurophysiological evidence of neural impairment.