A 69-year-old male, with a history of obesity and bronchiectasis, presented to Internal Medicine consultation to study abdominal adenopathies documented incidentally on abdominal ultrasound three years before. He had already been submitted to endoscopic ultrasound guided biopsy, which was inconclusive. Blood count, serum angiotensin converting enzyme, interferon-gamma release assay (IGRA) and protein electrophoresis were normal. HIV serology was negative, diabetes was excluded and the patient had no history of exposure to tuberculosis. Chest X-ray was normal. By the time of the first appointment the patient was asymptomatic but six months later he started complaining of dizziness and loss of balance. Positron emission tomography showed hypermetabolic adenopathies in multiple body compartments, including the abdomen, and a focal area on the right hemi cerebellum (Figure 1). MRI scan of brain was performed and a lesion involving the right cerebellar hemisphere and vermis with perilesional edema and mass effect was found. The biopsy revealed granulomas with central areas of necrosis (Figure 2A-B). Even though mycobacteria could not be identified in this sample or in the sputum, neither by culture or nucleic acid amplification (NAA), it was decided to start the patient on multiple drug therapy for tuberculosis (isoniazid, rifampicin, pyrazinamide, and ethambutol), with improvement.

Despite the decreasing prevalence and mortality of tuberculosis, it is still a non-negligible problem across the globe and the second most deadly infectious agent in the world [1]. Extra pulmonary tuberculosis may have an indolent course and clinical manifestations vary considerably depending on the location, even when central nervous system is affected [2]. The gold standard for the diagnosis of Mycobacterium tuberculosis infection is culture identification. However, in extra-pulmonary tuberculosis its sensitivity ranges between 0–80%. Other methods, such as smear microscopy, NAA tests and IGRAs also have high variability [3]. Although IGRA assays have shown good results in the diagnosis of active tuberculosis in Bacillus Calmette-Guérin vaccinated populations, factors associated with negative results (such as age > 50 and male gender) have been identified and should be taken into account [4].

This report illustrates that the diagnosis of tuberculosis remains a challenge, not only because of its silent course but also due to the suboptimal diagnostic tests available. Although there was no identification of Mycobacterium tuberculosis in our patient, the exclusion of a more probable diagnosis and the risk of not treating a tuberculoma, led to the decision to start tuberculosis treatment.

Keywords: Extra pulmonary tuberculosis, Tuberculoma, IGRA assay

We would like to thank Dr. Olinda Rebelo (Neuropathology Laboratory, Neurology Department, Coimbra Hospital and Universitary Centre) for providing histologic images.

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