PulmonaryMycobacterium kansasiiInfection Mimicking Malignancy on the¹⁸F-FDG PET Scan in a Patient Receiving Etanercept: A Case Report and Literature Review

Abstract

A 66-year-old male presented with chest pain, malaise, generalized weakness, and weight loss. He had been receiving etanercept injection for rheumatoid arthritis. Chest X-ray revealed a right upper lobe mass. Chest computed tomography (CT) showed a right apical mass, highly suggestive of a Pancoast tumor. The thoracic fluorine-18 fluoro-deoxy-glucose (18F-FDG) positron emission tomography (PET) scan demonstrated significantly high metabolic pulmonary lesions with the standardized uptake value (SUV) of 12.5, consistent with lung cancer. The patient underwent bronchoscopy and bronchoalveolar lavage (BAL). BAL cytology was negative for malignant cells. BAL acid fast bacilli (AFB) smears were positive, and Mycobacterium kansasii was eventually isolated. He received a 12-month course of rifampin, isoniazid, and ethambutol. Interval resolution of pulmonary lesions was noted on follow-up serial CT chest studies. There has been increasing incidence of nontuberculous mycobacterial infections reported in patients treated with the antitumor necrosis factor-alpha (anti-TNF-alpha) agents. Infectious foci have an increased glucose metabolism which potentially causes a high FDG uptake on the 18F-FDG PET scan, leading to undue anxiety and cost to the patients. This is the first reported case of pulmonary M. kansasii infection with a positive thoracic 18F-FDG PET study mimicking malignancy in a patient on etanercept.

Mycobacterium Kansasii infection in a psoriasis patient treated with adalimumab and switch to apremilast: first report and literature review

“…4,5 In the United States, infection with M. kansasii is the second most common cause of NTM after M. avium intracellular infection. 6 Anti-TNF-α agents are widely used to treat chronic inflammatory diseases; among well-known side effects, they may inhibit the orderly recruitment of cells necessary for the proper granuloma formation and the containment of intracellular pathogens. 7 Therefore, anti-TNF-α may lead patients to be more susceptible to mycobacterial infections and, in particular, to TB reactivation.…”

“… 4 , 5 In the United States, infection with M. kansasii is the second most common cause of NTM after M. avium intracellular infection. 6 …”

“… 6 Min and Amlani described a patient with rheumatoid arthritis receiving etanercept that developed M. kansasii lung infection. 6 Fernández-Guerrero reported a patient with ankylosing spondylitis treated with infliximab and also M. kansasii lung infection isoniazid-resistant. 14 Spiliopoulou et al reported a patient with sarcoidosis initially treated with etanercept then switched to infliximab; this patient presented also skin manifestations constituted by confluent vesicles and bullae on the dorsum of the left foot with underlying erythema and oedema.…”

“…4 To our knowledge, in the English literature only four case reports of M. kansasii infection under anti-TNF-α treatment (two with etanercept, two with infliximab, none with adalimumab) have been reported. 6 Min and Amlani described a patient with rheumatoid arthritis receiving etanercept that developed M. kansasii lung infection. 6 Fernández-Guerrero reported a patient with ankylosing spondylitis treated with infliximab and also M. kansasii lung infection isoniazid-resistant.…”

PET Metabolic Biomarkers for Cancer

“…For example, 18 F-FDG uptake is important in granulocytes and mononuclear cells of the immune system during infectious or inflammatory processes because of high energy demands. 22 Radiation therapy will also cause an uptake of 18 F-FDG in the treatment region. 23 On the other hand, tumors with low metabolic rates, such as the mucinous adenocarcinomas, or weak glucose avidity, such as some prostate cancers, can be associated with equivocal or negative scans.…”