Herein, we have described the rare clinical course of listeriosis. Two important insights were gained from this case: first, listeriosis can cause lesion formation in the adrenal glands; second, its clinical presentation may be difficult to differentiate from that of malignancy, on imaging studies.
Invasive listeriosis occurs at a frequency of 3–6 cases per 100,000 population, and in Japan, where this case occurred, the frequency is estimated at 6.5 cases/100,000 people [6,7,8]. Although it occurs more frequently in the elderly and in patients with underlying diseases, most cases present with a clinical picture of meningitis or bacteremia, and cases of space-occupying lesions in specific organs are rare. Patients with rheumatoid arthritis are known to be at a high risk of developing and dying from listeriosis, with the clinical picture being mainly bacteremia and meningitis, followed by arthritis and osteomyelitis [9, 10]. To the best of our knowledge, there have been no previous reports of abscess formation in the adrenal gland, as in the present case.
L. monocytogenes can invade the intestinal tract and enter the bloodstream, where it is mostly trapped by the Kupffer cells of the liver and spleen . Some bacteria survive, thus leading to bacteremia and meningitis, and rarely to localized lesions. In this patient, lower gastrointestinal endoscopy showed evidence of ileitis. Since the adrenal gland contained the largest lesion, we speculated that Listeria entered the bloodstream from the intestinal tract and formed a lesion in the adrenal gland followed by the spread to the liver and bone. In response to Listeria invasion, the host induces activation of immune cells, mainly macrophages, via interleukin-18 and interferon gamma (IFN-γ) [12, 13]. The immune response of the T-cells is essential for the production of IFN-γ and for the activation of macrophages, and the reduced functioning of macrophages leads to increased susceptibility to Listeria . Biological agents and immunosuppressive drugs used in this patient likely resulted in a markedly reduced cellular immune response; this may have led to a reduction in the ability of macrophages to eliminate organ-infiltrating Listeria, resulting in an increase in local abscess lesions.
In our case, Listeria bacteremia was confirmed; with continued antimicrobial therapy, the systemic lesions gradually shrank and eventually disappeared. Although the biopsy tissue did not confirm the organism because antimicrobial agents had already been administered, the clinical course clearly indicated that the patient had a unifying condition caused by L. monocytogenes.
In this case, the listeriosis resulted in the formation of a mass in the adrenal gland. Usually, mass formation in the adrenal gland is asymptomatic and discovered incidentally, and the cause is usually a noninfectious disease such as adrenal adenoma, cancer metastasis, pheochromocytoma, or hematoma . The infections that can involve the adrenal gland are diverse, including viral, fungal, bacterial, and parasitic infections . Space-occupying lesions such as abscesses, however, are rare. Histoplasmosis, paracoccidioides, and tuberculosis are known to produce granulomatous lesions in the adrenal glands, and some other infections such as disseminated nocardia have been reported to cause adrenal lesions [16, 17]. The initial diagnosis in this case was systemic metastasis of adrenal carcinoma. The fact that adrenal carcinoma is difficult to distinguish from abscesses on imaging  and that there were findings in the liver and bone on PET-CT may have accounted for the patient's listeriosis being a great mimicker of malignancy. Actinomycosis, nocardiosis, and mycosis have been reported to form foci reminiscent of malignancy, but all of these diseases are chronic infections [18,19,20,21]. We found only one report of multiple liver abscesses in an asymptomatic patient , but most listeriosis patients have symptoms such as fever, and follow an acute course. Our patient reported weight loss, but the cause was unclear; thus, it was not known how long the listeriosis had existed. There may be patients who develop slowly progressive listeriosis with few symptoms; however, further accumulation of such cases is necessary.
In conclusion, we encountered a case of listeriosis that had to be differentiated from adrenal carcinoma with multiple metastases. The patient was successfully diagnosed with listeriosis due to the proper collection of blood cultures prior to antimicrobial administration and absence of malignant findings on biopsy. Aggressive biopsy and microbiological examination should be considered in the presence of a space-occupying lesion of undetermined cause, especially in immunocompromised patients.