A 34-year-old female patient began experiencing unexplained fever 24 days ago, with no apparent triggers. Her highest recorded temperature reached 37.5℃ and was accompanied by symptoms including headache, fatigue, dyspnea, and joint pain. She denied having a cough or producing sputum. The patient found relief from these symptoms and returned to normal body temperature after taking acetaminophen tablets. However, the fever reoccurred six hours after taking the medication. Ten days ago, she sought medical attention at a local hospital, where her blood test revealed a leukocyte count of 2.81×10^9/L. Nucleic acid tests for both the novel coronavirus and influenza A virus returned negative results, as did the agglutination test for Borrelia burgdorferi bacteria. She was subsequently admitted to our hospital under the diagnosis of "fever of unknown origin." The patient had a previous history of good health and denied any recent travel, exposure to pastoral settings, or tick bites.
Physical Examination Findings
Upon examination, the patient exhibited the following vital signs: a temperature of 38.5°C, a pulse rate of 121 beats per minute, a respiratory rate of 23 breaths per minute, a blood pressure reading of 112/62 mmHg, and oxygen saturation levels at 98%. Notably, the physical examination did not reveal any abnormalities.
Diagnostic Studies
Blood routine showed WBC (White Blood Cell count): 2.67×109/L, Hb (Hemoglobin): 122g/L, PLT (Platelet count): 250×109/L, N% (Neutrophil percentage): 64.4%, ESO% (Eosinophil percentage): 0%. CRP (C-reactive protein): 6mg/dL; PCT (procalcitonin): 0.14ng/mL. Blood biochemistry, coagulation profile, and cardiac enzyme panel showed no significant abnormalities. Tumor markers and autoantibody tests came back negative.
The peripheral blood smear indicates a decrease in white blood cells and an increased proportion of neutrophilic rod-shaped granulocytes (28%). Bone marrow aspiration biopsy did not reveal any significant abnormalities.
During the hospitalization, we conducted multiple tests for the novel coronavirus nucleic acid, and the results were negative. The Monospot test and the Widal test came back negative, and multiple blood cultures have shown negative results.
Whole-body superficial lymph node ultrasound did not reveal any enlarged lymph nodes, and both cranial MRI and full-body CT scans came back normal. So, a PET/CT scan was arranged, but it still did not provide any diagnostic clues.
In order to rule out infectious diseases, we conducted a blood Next-Generation Sequencing (NGS) test, and the result was Covid-19 positive with a sequence count of 2000. We conducted a second round of COVID-19 nucleic acid testing, and the result was negative. The COVID-19 antibody test showed elevated levels of total Ig (251.36 COI), IgG (4.46 COI), and negative for IgM (0.14 COI).
Since the nucleic acid test were consistently negative but the blood NGS and antibody tests were positive, the diagnosis of long COVID was considered. Apart from providing supportive treatment, the patient was administered intravenous methylprednisolone, starting with a dose of 160mg. The patient's body temperature returned to normal. The methylprednisolone treatment was gradually reduced and completely stopped after three weeks, and the patient no longer had a fever. During the one-month follow-up after discharge, the patient's general condition was good, and at the six-month follow-up, the patient remained asymptomatic.