A few reports of patients with COVID-19 have been described by 18F-FDG PET/CT, mostly symptomatic patients with COVID-19 respiratory disease that include dry cough, shortness of breath and fever [5-7, 10-13]. However, a wide range of symptoms have been reported, ranging from asymptomatic or mild symptoms [8,12] to severe illness [5, 7, 11, 13]. These symptoms may appear at 2 to 14 days after exposure to the coronavirus SARS-CoV-2. The spectrum of clinical manifestations includes chills, myalgia, fatigue, headache, sore throat, loss of taste or smell, pressure in the chest, pleuritic pain, and rarely, digestive and neurological symptomatology [1, 2, 5, 13].
Pre-existing illnesses that put patients at higher risk include cardiovascular disease, diabetes, chronic respiratory disease, hypertension and immunodepression, according to the literature [2, 5, 14].
Nucleic acid testing (RT-PCR) is the gold standard for the diagnosis of COVID-19 infection, highly specific with a lower false positive rate. However, a high false negative rate has been described [3]. So, RT-PCR may give false-negative results about 30% of the time, if the test is obtained too early or too late compared to infection, or if the sample is not obtained or processed correctly [4].
Chest high-resolution CT is the routine-preferred method for screening, diagnosis, course severity assessment, and efficacy monitoring of COVID-19 pneumonia. CT findings of COVID-19 pneumonia have been widely reported. In the early stage, single or multiple masses or segmental ground-glass opacities (GGOs) can be found in the lung, mainly peripheral and bilateral, usually involving the lower lobes [3, 10]. However, some studies have reported a clinical-radiological mismatch between radiological patterns and symptomatology [8, 12]. In addition, not all in-patients are tested for COVID-19 before they are sent to the department for scans. The frequency of CT findings is related to the infection time course, and based on the current evidence, there are ground-glass abnormalities in the early disease phase, followed by crazy paving and increasing consolidation later in the disease course [3, 10]. Moreover, the reported sensitivity of chest CT in detecting COVID-19 at the initial presentation is 56-98% during the early stages of disease development and the specificity is low [4].
Recently, a few reports have been described the FDG avidity of that lung lesions with a SUVmax range between 4.6 and 12 g/ml [6]. PET/CT in our case, identified FDG-avid FDG-positive GGOs and consolidation in both lungs and also showed the lymph nodes FDG uptake. Although lymph node enlargement on CT is rare, lymphadenopathy is present in more than 1% of patients and mediastinal lymph node uptake has been observed by other authors [5].
COVID-19 may cause mostly lung inflammation but also address possible inflammatory involvement of myocardium, pericardium, muscles, intestine and the CNS. Hence, damage to other organs such as the gastrointestinal tract, heart, kidneys or bone marrow can occurred [2, 5, 14]. Abnormal coagulation parameters like a high D-Dimer level are associated with poor prognosis [14].
Finally, other pathologies and radiological findings do not exclude COVID-19 disease.