18F-FDG PET and PET/CT in Diagnosis and Treatment Monitoring of Pyrexia of Unknown Origin Due to Tuberculosis with Prominent Hepatosplenic Involvement

Usefulness of 18FDG-PET/CT and MRI in an immunocompetent patient with fever of unknown origin and following diagnosis of skeletal tuberculosis

INTRODUCTION

Fever of unknown origin (FUO) is one of the most difficult diagnostic dilemmas in current medicine. The main causes of FUO in developed countries are non-infectious inflammatory diseases, while infections are predominant in developing countries. Among infections, Mycobacterium Tuberculosis (TB) is the most frequent cause and it can involve multiple tissues and organs.

CASE AND OUTCOMES

We report a case of FUO in an immunocompetent patient with fever of unknown origin, finally diagnosed with skeletal TB thanks to a multidisciplinary approach, using FDG-PET/CT, MRI, and biopsy. PET/CT findings were non-specific (infection or inflammation versus malignancy); therefore, hip Magnetic Resonance Imaging (MRI) was performed and infection was suspected on basis of MRI findings, so a bone biopsy was then performed and skeletal TB was diagnosed.

DISCUSSION

A successful diagnostic workup of FUO has to take into account detailed medical history, physical examination, laboratory tests, blood and urine cultures, and standard imaging (Ultrasonography, CT, or MRI). However, this combination of clinical evaluation, standardized laboratory tests and simple imaging procedures often do not lead to a definite diagnosis; ⁸F-FDG-PET-CT could be performed to help in diagnosis and also to guide additional diagnostic tests such as MRI and biopsy.

CONCLUSION

This case demonstrates the importance of the integration of different imaging modalities, in particular, MRI and FDG-PET/CT in patients with FUO. Skeletal TB should always be included in the diagnostic hypothesis of FUO, even in immunocompetent patients of non-endemic countries.

The Peripheral Blood Transcriptome Is Correlated With PET Measures of Lung Inflammation During Successful Tuberculosis Treatment

Pulmonary tuberculosis (PTB) is characterized by lung granulomas, inflammation and tissue destruction. Here we used within-subject peripheral blood gene expression over time to correlate with the within-subject lung metabolic activity, as measured by positron emission tomography (PET) to identify biological processes and pathways underlying overall resolution of lung inflammation. We used next-generation RNA sequencing and [¹⁸F]FDG PET-CT data, collected at diagnosis, week 4, and week 24, from 75 successfully cured PTB patients, with the [¹⁸F]FDG activity as a surrogate for lung inflammation. Our linear mixed-effects models required that for each individual the slope of the line of [¹⁸F]FDG data in the outcome and the slope of the peripheral blood transcript expression data correlate, i.e., the slopes of the outcome and explanatory variables had to be similar. Of 10,295 genes that changed as a function of time, we identified 639 genes whose expression profiles correlated with decreasing [¹⁸F]FDG uptake levels in the lungs. Gene enrichment over-representation analysis revealed that numerous biological processes were significantly enriched in the 639 genes, including several well known in TB transcriptomics such as platelet degranulation and response to interferon gamma, thus validating our novel approach. Others not previously associated with TB pathobiology included smooth muscle contraction, a set of pathways related to mitochondrial function and cell death, as well as a set of pathways connecting transcription, translation and vesicle formation. We observed up-regulation in genes associated with B cells, and down-regulation in genes associated with platelet activation. We found 254 transcription factor binding sites to be enriched among the 639 gene promoters. In conclusion, we demonstrated that of the 10,295 gene expression changes in peripheral blood, only a subset of 639 genes correlated with inflammation in the lungs, and the enriched pathways provide a description of the biology of resolution of lung inflammation as detectable in peripheral blood. Surprisingly, resolution of PTB inflammation is positively correlated with smooth muscle contraction and, extending our previous observation on mitochondrial genes, shows the presence of mitochondrial stress. We focused on pathway analysis which can enable therapeutic target discovery and potential modulation of the host response to TB.

Defining 'Satisfactory Response' to Therapy in Abdominal Tuberculosis: A Work in Progress

Abdominal tuberculosis is difficult to diagnose due to low sensitivity of microbiological tests and the low histological yield. Satisfactory response to therapy has long been used a criteria for the diagnosis of abdominal tuberculosis. However, the appropriate definitions of response to therapy in abdominal tuberculosis have remained unclear. Recent evidence suggests that mucosal healing of ulcers at the end of therapy or at two months (early mucosal response) is a helpful criteria of response to therapy. This also helps in exclusion of multidrug resistant tuberculosis and alternative diagnosis like Crohn's disease. Further limited literature suggests the use of some biomarkers like C-reactive protein in the follow-up of patients with peritoneal or intestinal tuberculosis.

18F-Fluorodeoxyglucose positron emission tomography and infectious diseases: current applications and future perspectives

PURPOSE OF REVIEW

18F-Fluorodeoxyglucose positron emission tomography/computed tomography is a well-established technique for diagnosis and management of a number of neoplastic conditions. However, in recent years the body of literature regarding its potential role in infectious diseases has progressively increased, with promising results.

RECENT FINDINGS

So far 18F-fluorodeoxyglucose positron emission tomography/computed tomography has a well-established role and is recommended by guidelines only in a few settings, such as prosthetic valve endocarditis, vascular device infections, and chronic osteomyelitis. However, even the lack of large, prospective randomized trials, an increasing number of small series and case reports suggest a potential role in the diagnosis, disease staging, and monitoring of treatment response of several other infective conditions.

SUMMARY

In this article, we summarize the available evidence and potential future applications of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in the diagnosis and management of infectious diseases.

Tubercular Meningitis and Lymphadenitis Mimicking a Relapse of Burkitt's Lymphoma on (18)F-FDG-PET/CT: A Case Report

Tuberculosis (TB) can present with various forms and can occasionally be mistaken for malignancy. Hereby, we report a 53-year-old man diagnosed and treated for Burkitt's lymphoma in 2009 who achieved a complete remission confirmed by a computed tomography (CT) scan. During the follow-up 2 years later, he complained of left hip pain that warranted investigation with magnetic resonance imaging and whole-body ¹⁸F-fludeoxyglucose-positron emission tomography (FDG-PET)/CT which showed a benign lesion in the left hip associated with multiple lymph nodes in the chest and abdomen not amenable for biopsy. A follow-up PET/CT scan a few months later showed intense tracer uptake in the lymph nodes with size progression and appearance of new lymph nodes suspicious of lymphoma relapse. The patient was asymptomatic, and all investigations including viral and connective tissue disease studies were negative. Also the tuberculin skin test and QuantiFERON were negative. Lymph node biopsy was planned; however, the patient presented a few days earlier with fever, headache and photophobia. Cerebrospinal fluid (CSF) examination confirmed meningitis with lymphocytic pleocytosis and elevated protein. The CSF Gram stain, culture, viral and acid-fast bacilli were negative. CSF flow cytometry and cytopathology confirmed polyclonal lymphocytosis and suggested reactive causes. CSF TB culture grew Mycobacterium tuberculosis. Mediastinal lymph node biopsy also confirmed TB lymphadenitis. Four antituberculosis drugs were started. One year later, a PET/CT scan showed regression of all the involved lymph nodes. This case highlights the importance of excluding TB in patients with suspected malignancy, especially if they belong to endemic regions, and the increasing role of ¹⁸F-FDG-PET/CT in the early detection of extrapulmonary TB.

[18F]FDG-PET/CT for the diagnosis of patients with fever of unknown origin

BACKGROUND AND AIMS

The diagnosis of patients with fever of unknown origin (FUO) remains a challenging medical problem. We aimed to assess the diagnostic contribution of 18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET)/computed tomography (CT) for the evaluation of FUO.

METHODS

We performed a 4-year retrospective single-center study of all hospitalized patients that underwent FDG-PET/CT for evaluation of FUO. The final diagnosis of the febrile disease was based on clinical, microbiological, radiological and pathological data available at the final follow-up. Predictors for a contributory exam were sought.

RESULTS

One hundred and twelve patients underwent FDG-PET/CT for the investigation of FUO in the years 2008-2012 and were included in the study. A final diagnosis was determined in 83 patients (74%) and included: infectious disease in 49 patients (43%), non-infectious inflammatory disease in 17 patients (16%), malignancies in 15 patients (14%), other diagnoses in 2 patients (1.7%), FUO resolved with no diagnosis and no evidence of disease during a 6-month follow-up in 23 patients (20%), and death with fever and with no diagnosis in 6 patients (5%). Seventy-four FDG-PET/CT studies (66%) were considered clinically helpful and contributory to diagnosis (46% positive contributory value and 20.5% contributory to exclusion of diagnosis). PET/CT had a sensitivity of 72.2%, a specificity of 57.5%, a positive predictive value (PPV) of 74.2% and a negative predictive value (NPV) of 53.5%. On multivariable analysis, significant predictors of a positive PET/CT contributory to diagnosis were a short duration of fever and male gender.

CONCLUSIONS

PET/CT is an important diagnostic tool for patients with FUO.

Endobronchial ultrasound-guided transbronchial needle aspiration in lung cancer diagnosis and staging

Lung cancer is one of the most prevalent types of cancer in the world. A complete diagnosis of lung cancer involves tissue acquisition for pathological subtype, molecular diagnosis and accurate staging of the disease to guide appropriate therapy. Real-time endobronchial ultrasound transbronchial needle aspiration (EBUS-TBNA) is minimally invasive and relatively safe procedure, which can be done on an outpatient basis under moderate sedation. EBUS-TBNA has been shown to be a safe modality to obtain tissue for diagnosis, staging and molecular profiling in lung cancer. EBUS-TBNA stands out in comparison with other modalities for tissue acquisition in lung cancer. EBUS-TBNA performed with the patient under moderate sedation yields sufficient tissue for sequential molecular analysis in most patients. In this review, we describe the role of EBUS-TBNA in various aspects of diagnosis and staging of lung cancer in the present era along with its future aspects.