Unveiling tuberculous pyomyositis: an emerging role of immune reconstitution inflammatory syndrome

Immune reconstitution inflammatory syndrome is recognized as a paradoxical worsening of preexisting or smoldering opportunistic infections in patients with human immunodeficiency virus on highly active antiretroviral therapy because of the recuperating of immune system. We report a 42-year-old man on antiretroviral therapy with silent mycobacterium tuberculosis pyomyositis presenting with characteristic clinical and imaging features of immune reconstitution inflammatory syndrome. Because tuberculosis pyomyositis is less recognized and may be easily overlooked in terms of protean manifestations in extrapulmonary tuberculosis spreading, such mycobacterial infection can bring about substantial morbidity and even mortality during the immune recovery phase. The worldwide incidence of human immunodeficiency virus combined with tuberculosis infection is skyrocketing; therefore, emergency physicians must keep a heightened awareness and proficiency of this emerging culprit to obviate unnecessary intervention, preserve organ function, and achieve better outcomes. A 42-year-old man presented to the emergency department with a 1-week history of debilitating focal swelling of the left buttock. He had blood transfusion-related human immunodeficiency virus (HIV) type 1 infection, and 1 month previously, unexplained weight loss developed and his plasma virus load increased to 1,075,865 RNA copies/mL with a CD4 T-cell count of 102/μL. Accordingly, highly active antiretroviral therapy with prophylactic cotrimoxazole was carried out. He recalled intermittent mild discomfort over the lateral aspect of his thigh for a few months. On physical examination, his body temperature was 38.6°C, and he had a tense, painful swelling extending from the left gluteal region to the middle-third of hamstring, coupled with enlarged, soft, and nontender left inguinal lymph nodes. Laboratory studies showed the following: hemoglobin, 10.2 g/dL; platelet count, 195 × 10⁹/L; leukocyte count, 8 × 10⁹/L; C-reactive protein, 4.6 mg/dL; and normal liver and renal functions. His CD4 T-cell count was increased (255/μL), with considerably reduced viral load (960 copies/mL). Plain chest radiograph was unrevealing. Concordant with contrast-enhanced computed tomography scanning (Fig. 1), microbiological and histopathological analyses were consistent with mycobacterium tuberculosis (TB) pyomyositis. The temporal association of worsening clinical manifestations during antiretroviral treatment (ART) supported the diagnosis of immune reconstitution inflammatory syndrome (IRIS). Surgical drainage with corticosteroids and standard quadruple-drug antituberculous regimen achieved complete resolution of pyomyositis. Immune reconstitution inflammatory syndrome is a well-recognized adverse consequence of restoration of pathogen-specific immune responses during the initial months of antiretroviral treatment. Through suppression of HIV replication, ART permits both quantitative and functional reconstitution of the immune system, thereby reducing the risk of new opportunistic infections and neoplasia [1]. However, albeit diminished, an appreciable risk of opportunistic infection persists during ART, especially during the first few months of treatment [2]. Tuberculosis is the most common opportunistic disease in HIV-infected patients during the initial months of ART and presents a great challenge to ART programs, potentially causing significant morbidity and mortality. The risk of TB decreases steeply during the first year of ART and is strongly associated with improving immune status [3]. However, the limited sensitive diagnostic tests for TB when applied to patients with advanced immunodeficiency further compounds the therapeutic strategy. Although heightened clinical vigilance may, at least in part, account for increased ascertainment of TB infection during the initial phase of ART, restoration of immune responses may cause subclinical TB to be unmasked [4]. Subclinical TB among patients entering ART programs provides much of the reservoir of infection that fuels the high rates of symptomatic TB presenting during early ART. Because ART-induced immune recovery is time dependent, progress to symptomatic disease during early ART in the context of persisting immunodeficiency may occur. Because immunopathologic host responses to mycobacterium TB are crucial to the clinical presentation of TB, the development of symptoms is a function of both mycobacterial antigen burden and the intensity and quality of the associated host inflammatory response. This inflammatory process may be augmented by immune-mediated liberation of mycobacterial antigen, further enhancing immune responses. In patients with subclinical TB, this would cause TB to manifest much sooner than would otherwise have occurred in the absence of ART [5]. On the contrary, in patients with advanced immunodeficiency, TB often has a fairly insidious onset. Therefore, across the spectrum of TB-related IRIS, the principal features mainly rest on shortening of the time to development of symptoms, increasing the rapidity of the initial onset of symptoms of TB, and increasing the intensity of clinical manifestations [6]. Because the optimal treatment of IRIS is unknown, the current choice is systemic corticosteroids. Moreover, because the commencement of ART during the intensive phase of antituberculous treatment in patients with coexistent TB and advanced immunodeficiency is associated with a high risk of IRIS, conversely, deferment of treatment is associated with a high risk of other acquired immunodeficiency syndrome-related complications and death [7]. The worldwide incidence of TB is increasing, and a significant rise in the extrapulmonary TB has been observed worldwide with the pandemic of HIV infection. Tuberculosis pyomyositis is rare and may be easily overlooked in terms of protean manifestations in extrapulmonary TB spreading [8]. Therefore, emergency physicians must keep a heightened awareness and proficiency of this emerging culprit to obviate unnecessary intervention, preserve organ function, and achieve better outcomes.