Answer to October 2021 Photo Quiz.

Abstract

We report an unusual pyomyositis with concomitant pulmonary lesions in an HIV-positive patient. Due to the difficulty of collecting sputum, gastric lavage was performed. The abscess in the leg was drained (Fig. 1B in photo quiz case presentation). The gastric lavage and the abscess drainage were analyzed using an acid-fast bacilli smear (Fig. 1C in photo quiz case presentation) and Xpert MTB/RIF assay. Gastric lavage, purulent drainage, and blood culture were positive for Mycobacterium tuberculosis. The typical formation of serpentine cords was demonstrated upon culture of abscess drainage (Fig. 1D in photo quiz case presentation). Gastric lavage was M. tuberculosis nucleic acid positive by Xpert MTB/RIF assay. The diagnosis of tuberculosis (TB) pyomyositis was confirmed. Anti-TB therapy (rifampin) was started. Pyomyositis is the accumulation of purulent material within individual muscle groups, and the most common organisms implicated in pyomyositis include Staphylococcus aureus (1). Typical cases of pyomyositis involve fever and pain, which are specific to a muscle group, generally the lower extremities (1, 2). TB pyomyositis, defined as M. tuberculosis infection of skeletal muscle, is more common in immunocompromised patients, but even in these patients, it is considered to be a rare extrapulmonary manifestation of TB. The clinical manifestations may be insidious, with nonspecific symptoms, such as fever, night sweats, malaise, and weight loss (3). Ohnishi et al. reported three cases of TB pyomyositis in women coinfected with TB/HIV with a CD4 below 200 cells/mm3 (4). Pathogenesis for TB pyomyositis can include contiguous spread, lymphatic or hematogenous spread, and direct inoculation (3, 5). We hypothesize that in this case it was a hematogenous spread because of the absence of trauma or infection, with no evidence of osteomyelitis. TB pyomyositis is very difficult to clinically diagnose and distinguish from other soft tissue diseases. Diagnosis depends on a high clinical suspicion of infection in a susceptible population. TB should be considered in patients who present with soft tissue swelling and pain, particularly if they have an abnormal chest X-ray (6). Drainage through surgery and aggressive anti-TB therapy is normally required (7). The case presented here is noteworthy given the rarity of this manifestation of TB and highlights the need for early diagnosis. With timely diagnosis and adequate clinical and surgical treatment, the prognosis is good. Prompt diagnosis requires a high index of suspicion, especially in immunocompromised patients. Fluid cultures should be sent for acid-fast bacilli staining (Fig. 1C in photo quiz case presentation) and culture (8). In laboratories serving areas of high M. tuberculosis incidence with limited economic resources, cord factor detection (Fig. 1D in photo quiz case presentation) is a fast and valid criterion for identifying these mycobacteria using liquid or solid medium (9).