Acute and chronic pain associated with leprosy

Assessment of neuropathic pain, functional activity limitation and quality of life of people affected by leprosy in an endemic area in Northeast Brazil: a cross-sectional study

BACKGROUND

This study investigated the prevalence of neuropathic pain (NP) among people affected by leprosy and its effects on functional limitation and health-related quality of life (HRQoL) in an endemic area in Northeast Brazil.

METHODS

This is a cross-sectional study of 122 leprosy patients. Functional limitation and HRQoL were assessed using the Screening of Activity Limitation and Safety Awareness (SALSA) and WHO Quality-of-Life (WHOQoL-BREF) scales, respectively. Participants were assessed for the presence of pain and completed the Douleur Neuropathique 4 and the Brief Pain Inventory scales.

RESULTS

The prevalence of NP was 59%. Participants with NP had higher SALSA scores than those without pain (median; IQR: 42; 32-49.5 vs 27.5; 24-34; p=0.002). Increasing SALSA scores were related to decreasing WHOQoL-BREF scores in the physical (r=-0.54; p<0.001), psychological (r=-0.33; p=0.002) and environmental (r=-0.22; p=0.01) domains, but not in the social domain (r=-0.14; p=0.10). Individuals with NP had the lowest scores in all domains compared with individuals without pain.

CONCLUSIONS

Appropriate tools and training of clinicians for diagnosing NP in leprosy patients are necessary for their appropriate management and better HRQoL outcomes.

A Computational Model for Pain Processing in the Dorsal Horn Following Axonal Damage to Receptor Fibers

Computational modeling of the neural activity in the human spinal cord may help elucidate the underlying mechanisms involved in the complex processing of painful stimuli. In this study, we use a biologically-plausible model of the dorsal horn circuitry as a platform to simulate pain processing under healthy and pathological conditions. Specifically, we distort signals in the receptor fibers akin to what is observed in axonal damage and monitor the corresponding changes in five quantitative markers associated with the pain response. Axonal damage may lead to spike-train delays, evoked potentials, an increase in the refractoriness of the system, and intermittent blockage of spikes. We demonstrate how such effects applied to mechanoreceptor and nociceptor fibers in the pain processing circuit can give rise to dramatically distinct responses at the network/population level. The computational modeling of damaged neuronal assemblies may help unravel the myriad of responses observed in painful neuropathies and improve diagnostics and treatment protocols.

Revised estimates of leprosy disability weights for assessing the global burden of disease: A systematic review and individual patient data meta-analysis

BACKGROUND

Leprosy is a chronic bacterial infection caused by Mycobacterium leprae, which may lead to physical disability, stigma, and discrimination. The chronicity of the disease and disabilities are the prime contributors to the disease burden of leprosy. The current figures of the disease burden in the 2017 global burden of disease study, however, are considered to be under-estimated. In this study, we aimed to systematically review the literature and perform individual patient data meta-analysis to estimate new disability weights for leprosy, using Health-Related Quality of Life (HRQOL) data.

METHODOLOGY/PRINCIPAL FINDINGS

The search strategy included all major databases with no restriction on language, setting, study design, or year of publication. Studies on human populations that have been affected by leprosy and recorded the HRQOL with the Short form tool, were included. A consortium was formed with authors who could share the anonymous individual-level data of their study. Mean disability weight estimates, sorted by the grade of leprosy disability as defined by WHO, were estimated for individual participant data and pooled using multivariate random-effects meta-analysis. Eight out of 14 studies from the review were included in the meta-analysis due to the availability of individual-level data (667 individuals). The overall estimated disability weight for grade 2 disability was 0.26 (95%CI: 0.18-0.34). For grade 1 disability the estimated weight was 0.19 (95%CI: 0.13-0.26) and for grade 0 disability it was 0.13 (95%CI: 0.06-0.19). The revised disability weight for grade 2 leprosy disability is four times higher than the published GBD 2017 weights for leprosy and the grade 1 disability weight is nearly twenty times higher.

CONCLUSIONS/SIGNIFICANCE

The global burden of leprosy is grossly underestimated. Revision of the current disability weights and inclusion of disability caused in individuals with grade 0 leprosy disability will contribute towards a more precise estimation of the global burden of leprosy.

TRPA1 as a therapeutic target for nociceptive pain

Introduction

Chronic pain affects approximatively 30–50% of the population globally. Pathologies such as migraine, diabetic neuropathy, nerve injury and treatment with chemotherapeutic agents, can induce chronic pain. Members of the transient receptor potential (TRP) channels, including the TRP ankyrin 1 (TRPA1), have a major role in pain.

Areas covered

We focus on TRPA1 as a therapeutic target for pain relief. The structure, localization, and activation of the channel and its implication in different pathways to signal pain are described. This paper underlines the role of pharmacological interventions on TRPA1 to reduce pain in numerous pain conditions. We conducted a literature search in PubMed up to and including July 2020.

Expert opinion

Our understanding of the molecular mechanisms underlying the sensitization of central and peripheral nociceptive pathways is limited. Preclinical evidence indicates that, in murine models of pain diseases, numerous mechanisms converge on the pathway that encompasses oxidative stress and Schwann cell TRPA1 to sustain chronic pain. Programs to identify and develop treatments to attenuate TRPA1-mediated chronic pain have emerged from this knowledge. Antagonists explored as a novel class of analgesics have a new and promising target in the TRPA1 expressed by peripheral glial cells.

Neuropathic Pain: From Mechanisms to Treatment

Neuropathic pain caused by a lesion or disease of the somatosensory nervous system is a common chronic pain condition with major impact on quality of life. Examples include trigeminal neuralgia, painful polyneuropathy, postherpetic neuralgia, and central poststroke pain. Most patients complain of an ongoing or intermittent spontaneous pain of, for example, burning, pricking, squeezing quality, which may be accompanied by evoked pain, particular to light touch and cold. Ectopic activity in, for example, nerve-end neuroma, compressed nerves or nerve roots, dorsal root ganglia, and the thalamus may in different conditions underlie the spontaneous pain. Evoked pain may spread to neighboring areas, and the underlying pathophysiology involves peripheral and central sensitization. Maladaptive structural changes and a number of cell-cell interactions and molecular signaling underlie the sensitization of nociceptive pathways. These include alteration in ion channels, activation of immune cells, glial-derived mediators, and epigenetic regulation. The major classes of therapeutics include drugs acting on α₂δ subunits of calcium channels, sodium channels, and descending modulatory inhibitory pathways.

Autophagy dysfunction in neuropathic pain

Autophagy is a lysosomal degradation pathway that maintains tissue homeostasis by recycling damaged and aged cellular components, which plays important roles in development of the nervous system, as well as in neuronal function and survival. In addition, autophagy dysfunction underlies neuropathic pain. Thus, the modulation of autophagy can alleviate neuropathic pain. Here, we describe the definition, mechanisms of autophagy and neuropathic pain. On this basis, we further discuss the role of autophagy dysfunction in neuropathic pain. This review updates our knowledge on autophagy mechanisms which propose potential therapeutic targets for the treatment of neuropathic pain.

Diagnosis and impact of neuropathic pain in leprosy patients in Nepal after completion of multidrug therapy

Objectives

Neuropathic pain (NP) can occur as a chronic complication of leprosy neuropathy. NP epidemiology and its impact on patients have not been well documented. This study investigates NP prevalence and impact in the years after patients are declared “released from treatment” (RFT) following multidrug therapy (MDT) completion.

Methods

In this cross-sectional study, 85 RFT patients were recruited within leprosy referral services in Nepal. The Douleur Neuropathique 4 Questionnaire (DN4) was used to screen for NP. Pain severity, impacts on patients’ daily activities and mental health were measured by using the Brief Pain Inventory (BPI), Screening of Activity Limitation and Safety Awareness (SALSA), and General Health Questionnaire-12 (GHQ-12) respectively.

Results

96% surveyed had been treated for multibacillary leprosy. 44 (52%) complained of pain of which 30 (68%) were diagnosed with NP. NP was not associated with age, gender, or presence of skin lesions or nerve symptoms at leprosy diagnosis. 70% of patients with NP had either history of or ongoing reactions and 47% had grade 2 disability. Nerve tenderness (p = 0.023) and current reactions (p = 0.018) were significant risk factors for NP. Patients with NP suffered significantly higher intensity pain (p = 0.023) and daily life interference (p = 0.003) and were more likely to have moderate to extreme daily activity limitations (p = 0.005). 13 (43%) exhibited psychological distress, and medications only reduced moderate degree (50–60%) of pain.

Conclusions

In our study, 35% of RFT patients had ongoing NP. Risk factors include nerve tenderness and reaction. They suffer from more daily life interference and psychological distress. Leprosy patient care should include recognition and management of NP.

Leprosy could present with chronic neuropathic pain, which might severely disturb daily life and mental health of leprosy-infected patients. This complication could also occur even years after antibiotics therapy completion, and we noticed that it is associated with recent leprosy reactions and nerve tenderness on physical examination. This is the first study that describes the epidemiology of neuropathic pain in leprosy patients in Nepal. More than one-third of leprosy patients who had completed multidrug therapy, are still suffering from neuropathic pain, and this study demonstrated that it has caused a great impact to their daily activities and psychological status. Therefore, prompt recognition and management of neuropathic pain are mandatory while taking care of the patients with leprosy.

Neuropathic pain

Neuropathic pain is caused by a lesion or disease of the somatosensory system, including peripheral fibres (Aβ, Aδ and C fibres) and central neurons, and affects 7-10% of the general population. Multiple causes of neuropathic pain have been described and its incidence is likely to increase owing to the ageing global population, increased incidence of diabetes mellitus and improved survival from cancer after chemotherapy. Indeed, imbalances between excitatory and inhibitory somatosensory signalling, alterations in ion channels and variability in the way that pain messages are modulated in the central nervous system all have been implicated in neuropathic pain. The burden of chronic neuropathic pain seems to be related to the complexity of neuropathic symptoms, poor outcomes and difficult treatment decisions. Importantly, quality of life is impaired in patients with neuropathic pain owing to increased drug prescriptions and visits to health care providers, as well as the morbidity from the pain itself and the inciting disease. Despite challenges, progress in the understanding of the pathophysiology of neuropathic pain is spurring the development of new diagnostic procedures and personalized interventions, which emphasize the need for a multidisciplinary approach to the management of neuropathic pain.

The paradox of painless periodontal disease

Periodontal diseases, primarily gingivitis and periodontitis, are characterised by progressive inflammation and tissue destruction. However, they are unusual in that they are not also accompanied by the pain commonly seen in other inflammatory conditions. This suggests that interactions between periodontal bacteria and host cells create a unique environment in which the pro-algesic effects of inflammatory mediators and factors released during tissue damage are directly or indirectly inhibited. In this review, we summarise the evidence that periodontal disease is characterised by an accumulation of classically pro-algesic factors from bacteria and host cells. We then discuss several mechanisms by which inflammatory sensitisation of nociceptive fibres could be prevented through inactivation or inhibition of these factors. Further studies are necessary to fully understand the molecular processes underlying the endogenous localised hypoalgesia in human periodontal disease. This knowledge might provide a rational basis to develop future therapeutic interventions, such as host modulation therapies, against a wide variety of other human pain conditions.

Agreement Between the Douleur Neuropathique in 4 Questions and Leeds Assessment of Neuropathic Symptoms and Signs Questionnaires to Classify Neuropathic Pain Among Patients with Leprosy

Neuropathic pain (NP) often occurs during the course of leprosy, and screening tools to differentiate NP from non-NP are often used. However, their performance varies in different settings. The most frequently used scales are the Douleur Neuropathique in 4 questions (DN4) and the Leeds assessment of neuropathic symptoms and signs (LANSS) questionnaires. Thus, we conducted a study to evaluate the agreement between DN4 and LANSS questionnaires to classify NP in 195 leprosy patients attending two reference centers in Sergipe, Brazil. The DN4 and LANSS classified 166 and 110 patients, respectively, as having NP. One hundred and seven (54.8%) were classified as NP by both questionnaires; 59 (30.2%) solely by the DN4 questionnaire and three (1.5%) solely by the LANSS. The agreement of the questionnaires was 66.2% (weak agreement, Kappa = 0.30). Although both questionnaires identified a high proportion of NP, the development of more robust instruments is necessary to ensure the accuracy of diagnosis of leprosy patients classified as having NP.

Pain and quality of life in leprosy patients in an endemic area of Northeast Brazil: a cross-sectional study

Background

Pain emerges as a challenge in the treatment of leprosy patients. In this study, we describe the prevalence and type of pain in patients with leprosy, and its effect on patients’ quality of life in an endemic area of Northeast Brazil.

Findings

A cross-sectional survey of 260 patients attending leprosy reference centres in Sergipe, Northeast Brazil was conducted. Individuals were assessed for the presence and type of pain, skin sensory loss, peripheral nerve enlargement, touch and pinprick sensations, mechanical allodynia and nerve palpation. Participants completed the Douleur Neuropathique 4 questionnaire, and we also used the Brief Pain Inventory scale and the World Health Organization Quality of Life-BREF instrument to arrive at our results. One hundred and ninety-five (75 %) patients reported pain, mostly of the neuropathic type. Pain was moderate in 84 (43.1 %) and severe in 94 (48.2 %) participants. The presence of pain was associated with disability (p = 0.001), leprosy reactions (p = 0.004) and lower quality of life. Most patients with neuropathic pain were treated with steroids, despite their low efficacy for this type of pain.

Conclusion

Pain is highly prevalent among leprosy patients and is associated with low quality of life. Leprosy management should include a systematic assessment of the type of pain a patient experiences in order to provide adequate treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0113-1) contains supplementary material, which is available to authorized users.

ENLIST 1: An International Multi-centre Cross-sectional Study of the Clinical Features of Erythema Nodosum Leprosum

Erythema nodosum leprosum (ENL) is a severe multisystem immune mediated complication of borderline lepromatous leprosy and lepromatous leprosy. ENL is associated with skin lesions, neuritis, arthritis, dactylitis, eye inflammation, osteitis, orchitis, lymphadenitis and nephritis. The treatment of ENL requires immunosuppression, which is often required for prolonged periods of time and may lead to serious adverse effects. ENL and its treatment is associated with increased mortality and economic hardship. Improved, evidence-based treatments for ENL are needed; however, defining the severity of ENL and outcome measures for treatment studies is difficult because of the multiple organ systems involved. A cross-sectional study was performed, by the members of the Erythema Nodosum Leprosum International STudy (ENLIST) Group, of patients with ENL attending seven leprosy referral centres in Brazil, Ethiopia, India, Nepal, the Philippines and the United Kingdom. We systematically documented the clinical features and type of ENL, its severity and the drugs used to treat it. Patients with chronic ENL were more likely to be assessed as having severe ENL. Pain, the most frequent symptom, assessed using a semi-quantitative scale was significantly worse in individuals with “severe” ENL. Our findings will determine the items to be included in a severity scale of ENL which we are developing and validating. The study also provides data on the clinical features of ENL, which can be incorporated into a definition of ENL and used for outcome measures in treatment studies.

Leprosy is caused by a bacterium and is curable with a combination of antibiotics known as multi-drug therapy, which patients take for six or 12 months. However, a significant proportion of leprosy patients experience severe inflammation in their skin, nerves and other organs known as erythema nodosum leprosum (ENL). ENL is a severe complication of leprosy which can occur before, during, or after completion of antibacterial treatment. ENL causes severe morbidity affecting not only the skin, but also bones, joints, eyes, nerves, testes and kidneys. ENL may be fatal and it has been shown that the adverse effects of corticosteroid treatment also contribute to mortality. An effective treatment for ENL is thalidomide but this is not available in many leprosy endemic countries or is severely constrained by availability, cost and justified concerns about teratogenicity. Thalidomide, despite its effectiveness, is rarely used as a first line agent. Other effective drugs need to be identified to reduce the burden of this condition. In order to establish which treatments will be effective in ENL it is necessary to have a clear picture of the clinical features of the disease and how these influence severity. This is the first systematic study of ENL to define these and will help in developing tools to facilitate treatment studies of this severe, debilitating complication of leprosy.