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Revista2Vol89ingles2_Layout 1 4/2/14 10:03 AM Página 219 219 CONTINUING MEDICAL EDUCATION s Cutaneous tuberculosis: epidemiologic, etiopathogenic and clinical aspects - Part I* Josemir Belo dos Santos1 Ana Roberta Figueiredo1 Cláudia Elise Ferraz1 Márcia Helena de Oliveira1 Perla Gomes da Silva1 Vanessa Lucília Silveira de Medeiros1 DOI: http://dx.doi.org/10.1590/abd1806-4841.20142334 Abstract: Cutaneous tuberculosis (CTB) is the result of a chronic infection by Mycobacterium tuberculosis, M. bovis and occasionally by the Calmette-Guerin bacillus. The clinical manifestations are variable and depend on the interaction of several factors including the site of infection and the host’s immunity. This article revises the current knowledge about this disease’s physiopathology and immunology as well as detailing the possible clin- ical presentations. Keywords: Erythema induratum; Mycobacterium tuberculosis; Tuberculosis; tuberculosis, cutaneous; Tuberculosis, lymphnode INTRODUCTION Cutaneous tuberculosis was a major public increase in the incidence amongst the natives (indige- health problem in the nineteenth and early twentieth nous population).4 centuries. With the improvement of hygiene habits in About 14% of the affected, corresponding to the general population, the improvement of living just over 10,000 patients, present extra-pulmonary standards, the use of the BCG vaccine, and the intro- forms. When it is assumed that 1-2% of those with duction of effective chemotherapy, there was a signif- extra-pulmonary forms have cutaneous involvement, icant decrease in the number of cases. From the mid- one can estimate about 100 to 200 new cases of cuta- twentieth century onwards, there was a resurgence of neous tuberculosis per year in Brazil.3 the disease with the main causes being the increased incidence of HIV-positive patients, the emergence of INFECTIOUS AGENT multidrug-resistant tuberculosis and the growing Cutaneous tuberculosis has as its main etiologic number of patients receiving immunosuppressive agent the Mycobacterium tuberculosis (Mtb) that belongs treatments.1,2 to the class Schizomycetes, order Actinomycetales, family Mycobacteriaceae and genus Mycobacterium. EPIDEMIOLOGY Occasionally it is also caused by M. bovis or BCG vac- Tuberculosis (TB) represents a major public cine (an attenuated strain of M. bovis).5 health problem in Latin America, since it affects all Mycobacterium tuberculosis is a straight or slight- countries in this macro region. It is estimated that in ly bent (rod-shaped), non-motile, non sporulated, 2011, the prevalence of TB in Bolivia was 209 per unencapsulated bacillus, measuring from 1 to 10μm 100.0003 representing the highest rate, while Uruguay long by 0.2 to 0.6μm wide; its most important feature had the lowest prevalence among South American is that it becomes stained in red by fuchsin and does countries with 22 per 100,000 inhabitants.3 Brazil is the not discolor under the actions of alcohol and acid 17th among 22 countries that concentrate 80% of the (acid-fast bacillus). Its cellular wall has a high lipid global burden of TB. In 2011, 71,000 new cases were content which grants resistance against the action of reported in Brazil, corresponding to an incidence rate chemical agents, though, it is susceptible to the action of 37.1 per 100,000 inhabitants.4 Areas considered of of physical agents (heat and ultraviolet radiation).5 low-incidence have rates lower than 25 per 100,000 This bacillus is a strict aerobic pathogen that inhabitants. Regarding gender, 66.5% of the cases in requires certain conditions to grow and multiply: oxy- Brazil occur in men and with respect to race there is an gen, nutrients and an adequate pH in the medium. It Received on 03.12.2012. Approved by the Advisory Board and accepted for publication on 10.04.2013. * Work performed at the Dermatology Clinic at Pernambuco Federal University Clinics Hospital (HC-UFPE) - Recife (PE), Brazil. Financial Support: None. Conflict of Interest: None. 1 Pernambuco Federal University (UFPE) – Recife (PE), Brazil. ©2014 by Anais Brasileiros de Dermatologia An Bras Dermatol. 2014;89(2):219-28. Revista2Vol89ingles2_Layout 1 4/2/14 10:03 AM Página 220 220 Santos JB, Figueiredo AR, Ferraz CE, Oliveira MH, Silva PG, Medeiros VLS has approximately 4,000 genes with most of them addition to the aforementioned, Th17 cells pathway involved in the mechanisms of immune system eva- stimulated by interleukins IL-17 and IL-23, has recent- sion. For example, 200 of the genes are involved in ly been studied and considered as an essential part in lipid metabolism. So much emphasis occurs because the inducement, formation and maintenance of gran- lipids are the main energy source of Mtb and therefore ulomas in the long-term.7,8 are directly responsible for its ability to multiply in Cutaneous tuberculosis can be acquired from host tissue and form cellular walls. It can also be con- hematogenous or lymphatic dissemination of a pul- sidered a facultative intracellular parasite, since it is monary focus or by direct inoculation. However able to survive and multiply both outside and inside whenever there is a new accretion of bacilli, the entire phagocytic cells.6 immunologic cascade will start again and continue until the formation of granulomas.10 IMMUNOPATHOGENESIS The immune response in tuberculosis occurs FACTORS INVOLVED IN DISEASE PROGRES- basically via Th1 pathway, with little or no involve- SION ment of Th2 pathway. After the mycobacteria are The development of clinical manifestations in inhaled, alveolar macrophages are activated, the cutaneous tuberculosis should be understood as the infectious agents are internalized and the bactericidal outcome of interactions between the environment, the apparatus, such as the generation of intermediate agent and the host. nitrogen compounds, is triggered in an attempt to A - Infected person’s cellular immunity state: eliminate the bacilli at that point.7,8 only 5-10% of people infected with the bacilli will If the mycobacteria survive, a second stage develop tuberculosis. The likely explanation for this is begins, in which they divide within the macrophages. the host’s ability to contain infection. In 2008, The latter are no longer able to eliminate the infectious Gaikwad and Sinha performed a study aiming to agents alone, so they induce the production of demonstrate the individual variation in the immune cytokines such as IL-6, IL-12, IL-1α and IL-1β, resulting response against Mtb, with volunteers living in an in the recruitment of monocytes, lymphocytes, neu- endemic region, immunized with BCG and presenting trophils and dendritic cells. CD4 +, CD8 + and NK-cell Mtb antibodies to confirm prior exposure. As the lymphocytes are stimulated by interleukins (IL-12 and blood of volunteers was exposed to Mtb, the intensity IL-18) produced by dendritic cells to release IFN-γ in of T-cell proliferation and levels of INF-γ and antibod- order to stimulate the production of RIN (Reactive ies were evaluated. Patients classified as strong Nitrogen Intermediates), ROI (Reactive Oxygen responders had high levels of antibodies against Mtb Intermediates) and TNF-α. The intensity of IFN-γ pro- cell membrane, high levels of INF-γ and IL-12 and duction is regarded today as an important marker of consequently low replication rates of opsonized bacil- effective immune response against Mtb (attenuated or li. The reverse was found in the other group, classified wild) and this is relevant for the development of new as weak responders.11 Another mechanism involved in diagnostic tests and vaccines for tuberculosis.7,8,9 natural immunity against Mtb, which possibly varies After the failure of the initial containment in intensity, is the apoptosis of infected macrophages mechanisms, the body begins a new attempt to control when the elimination of mycobacteria is no longer the growth of mycobacteria population through gran- possible. The greater capacity for apoptosis is associ- ulomas stimulated by TNF-α.10 Once again, the release ated with high levels of prostaglandin E2 and con- of IL-1, IL-6, RNI, and ROIs by the macrophages will versely low levels of lipoxin A4.12 be triggered. The chronic presence of these inter- Analogous to leprosy, in 1994 Sehgal et al.5 leukins stimulating macrophages will ultimately attributed a spectral character to cutaneous tuberculo- cause their differentiation into epithelioid and giant sis, based on bacteriological, histopathological and cells that will organized themselves, to greater or less- immunological parameters. Some case reports er extent, into granulomas according to individual describe the patterns of the predominant cytokines for host factors. Laboratory animals with TNF-α deficien- each clinical form, such as lupus vulgaris and tubercu- cy fail to form effective granulomas, confirming its impor- losis verrucosa cutis, however there are still no com- tance to the efficacy of cellular response.7,8 parative studies showing variance in the immune sta- Containment will lead to stabilization, infection tus in different forms of TB.9,10 latency or cure, whereas non-containment will cause B – Infection route: the route of infection, the tissue damage and dissemination. Over time, Mtb presence or absence of prior contact with the bacilli persistence inside the granuloma, associated with plus the individual’s natural immune response are all possible failures in the immune system, keep the decisive factors in the disease clinical presentation. chances of focal reactivation a constant concern. In According to the infection route, cutaneous tuberculo- An Bras Dermatol. 2014;89(2):219-28. Revista2Vol89ingles2_Layout 1 4/2/14 10:03 AM Página 221 Cutaneous tuberculosis: epidemiologic, etiopathogenic and clinical aspects - Part I 221 sis can be acquired by exogenous or endogenous mech- in establishing resistance to antibiotics (isoniazid and anisms. Exogenous infection results from direct inocu- ethambutol) and the direct virulence of bacilli (sur- lation of bacilli into the skin of susceptible individuals vival capacity), depending on the point at which (tuberculous chancre, tuberculosis verrucosa cutis).