Necrotizing Cervical Lymphadenitis Caused by Mycobacterium simiae in an HIV-Positive Patient: Imaging with 18F-FDG PET/CT

Abstract

Mycobacterium simiae (M. simiae) is an opportunistic pathogen rarely associated with human disease, although in recent years M. simiae has been detected with increasing frequency in human immunodeficiency virus (HIV)-infected patients, usually causing disseminated infection with fever, diarrhea and weight loss. We report the case of an HIV-positive man, who was referred for an 18 F-FDG PET/CT to evaluate a solitary pulmonary nodule. The PET/CT showed incidental large necrotic cervical lymph nodes, compatible with necrotizing cervical lymphadenitis. Biopsy and culture of one of the affected lymph nodes were positive for M. simiae. We present the first report of 18 F-FDG PET/CT imaging of an infectious process caused by M. simiae in humans.Keywords Mycobacterium simiae . Necrotizing cervical lymphadenitis . Fluorodeoxyglucose . PET/CT . HIV Case ReportA 43-year-old HIV-positive man presented with a 2-week history of fevers and sore neck. His blood tests had shown: absolute CD4 count of 170 cells/ul (normal 420-1,980), absolute CD8 count of 966 cells/ul (normal 160-990), CD4/CD8 ratio 0.20 (normal 1.0-2.3) and WBC 13.3×10 9 (normal 4.0-11.0 ×10 9 , 62% neutrophils, 21% lymphocytes, 11% monocytes and 1% eosinophils). A contrast-enhanced CT of the neck showed mildly enlarged bilateral cervical lymph nodes at level 2A, the largest measuring 2.5 cm×2.0 cm on the left and 1.6 cm×1.5 cm on the right (Fig.

Mycobacterium simiae: Harmless colonizer or deadly pathogen?

“…simiae can also cause various focal infections [20]. Cases of osteomyelitis in the spine, pelvis, and femur [5], genitourinary infections [5], lymphadenitis [6], meningitis [8], and skin and soft tissue infections [23] have been reported.…”

“…M. simiae is a slow-growing photochromogenic mycobacterium that was initially considered an environmental pathogen mainly acquired from water [2,4]. This organism can be found in municipal water sources [5], as well as soil, salt, foodstuff, and even air samples [6]. It has been identified in hospital drinking fountains, sinks, and ice machines and can act as a reservoir for nosocomial M. simiae outbreaks [2].…”

Kikuchi Disease Mimicking Metastatic Lymphadenopathy on 18F-FDG PET/CT in Patients with Breast Cancer

“…[3][4][5][6][7][8], which reported having definite FDG uptake in affected LNs and receiving helpful information from the histologic diagnosis on the distribution and metabolic activity of regional or generalized LAPs or recurrence.…”