A 61-year-old female with chills and fever was admitted to the emergency department of the first affiliated hospital of Zhejiang university school of medicine on December 27, 2021. She developed a sudden fever of 39.4 C with no apparent cause, accompanied by chills, malaise, cough, and a small amount of white mucous sputum. She had a history of rheumatoid arthritis for more than 15 years and had taken methylprednisolone (2 mg, twice a day) since then. She was diagnosed with allergic vasculitis about one year ago and the dosage of methylprednisolone was adjusted to 16 mg, twice a day. She had skin ulcers on her lower extremities one month before admission, and after regular treatment, the skin ulcers seemed healed upon admission to our emergency department.
Laboratory findings upon admission to the emergency department were shown as follows: white blood cell, 21.52x109/L; neutrophils, 91.1%; lymphocytes, 5.5%; red blood cell, 4.33x1012/L; hemoglobin, 118 g/L; platelet, 172x109/L; C-reactive protein, 129.97 mg/L; and procalcitonin, 2.45 ug/L. Other laboratory results were within the normal range. The chest computed tomography (CT) demonstrated multiple nodular foci with partial cavitations in the lower lobes of both lungs (Figure 1A).
Given the possibility that the above findings were caused by infection, the patient was then transferred to our respiratory ward for further treatment. Her vital signs were shown as follows: temperature, 36.2 C; blood pressure, 112/60 mmHg; pulse rate, 84 beats/min; and respiration rate, 20 breaths/min. She was conscious with no systemic symptoms. The chest CT demonstrated small nodules and pulmonary bullae in the right lower lung (Figure 1B). The abdominal enhanced CT showed a low-density focus in the right abdominal wall, small stones in the left kidney, a small amount of pelvic fluid, and low-density nodules next to the upper pole of the right kidney. The result of blood next-generation sequencing (NGS) from the emergency room revealed Nocardia farcinica (Table 1). Staphylococcus aureus and Nocardia farcinica were found in sputum culture. Antibiotic susceptibility testing revealed that the cultured bacterium was sensitive to trimethoprim-sulfamethoxazole (TMP-SMX), amikacin, linezolid, and imipenem (Table 2). Cryptococcus neofermans capsule antigen, fungal D-glucan, T-cell and gene Xpert for tuberculosis, autoantibodies, and rheumatoid factor tests were all negative. To counteract the infection, the patient was treated with TMP-SMX, linezolid, and imipenem based on the antibiotic susceptibility test. Given the patient's occult blood in the stool, the hormone was suspended on the advice of gastroenterology, rheumatology, and immunology consultants. On December 31, 2021, the patient experienced a sudden generalized seizure with loss of consciousness for approximately one minute. Her airway was immediately opened, and midazolam was used for anti-epilepsy. The brain-enhanced magnetic resonance imaging (MRI) revealed nodular and patchy abnormal signal lesions with clear boundaries were found in the left frontal lobe and right basal ganglia, and that the lesions appeared gyri-form, ring-like, and inhomogeneous after enhancement. The largest lesion was approximately 4.7x3.5 cm with a low signal on T1WI, a high signal on T2WI, and an inhomogeneous high signal on FLAIR (Figure 2A).  
The patient was diagnosed with disseminated nocardiosis and then transferred to the intensive care unit (ICU). In the ICU, she was performed with ventilator-assisted ventilation (BIPAP mode: FiO2, 25%; peak airway pressure, 20 cmH2O; PEEP, 5 cmH2O). The cerebrospinal fluid (CSF) test showed: pressure, 250 mmH2O; colorless and clear; Pan's test negative; erythrocytes, 40/L; nucleated cells, 2/L; chlorine, 122 mM; glucose, 3.2 mM; and protein, 0.36 g/L. The Cryptococcus neoformans capsular antigen and tubercle Bacillus tests in both CSF and blood were negative. Nocardia farcinica was also found positive in bronchoalveolar lavage fluid (BALF). Mycobacterium tuberculosis was negative in the sputum and the BALF. The patient was continuously given TMP-SMX, imipenem, and amikacin. Simultaneously, she was administered levetiracetam and topiramate for counteracting epilepsy, and mannitol for reducing intracranial pressure. During her 10-day stay in the ICU (from December 31, 2021 to January 10, 2022), the patient had no seizures but had a persistent fever (the highest body temperature was 39.4 C) and a large amount of yellow purulent sputum. Auscultation of both lungs revealed sporadic moist rales. The chest CT on January 10, 2022 revealed multiple nodules with partial cavities and lung vasculitis in both lungs (Figure 3A). In multi-repeated sputum cultures, Nocardia farcinica, Aspergillus flavus, and Burkholderia neocepacia were discovered (Table 3). Considering the progression of vasculitis and exudative lesions in lungs, a tracheotomy was performed and the ventilator parameters were adjusted (BIPAP mode: FiO2, 45%; peak airway pressure, 26 cmH2O; PEEP, 8 cmH2O). Amikacin was then suspended, and voriconazole was added for antifungal therapy. Since the patient had a history of allergic vasculitis, she was given methylprednisolone (40 mg, intravenously every 12 h) and mannitol (20 g, intravenously every 12h). Until January 17, 2022, the patient had no fever or seizures, and showed a great improvement in pulmonary ventilation function. The brain and chest CT on January 17, 2022 revealed a low-density lesion in the left frontal lobe of the brain and multiple infectious lesions accompanied by local cavities in both lungs (Figure 3B). Compared with the chest CT images on January 10, 2022 (Figure 1A), those on January 17, 2022 indicated a great alleviation of pulmonary infection in this patient (Figure 3B). The antibiotic regimen was then adjusted to TMP-SMX, linezolid, voriconazole, and methylprednisolone without mannitol. The patient was performed with high flow-assisted ventilation (oxygen concentration, 30%; flow rate, 50 L/min) after a spontaneous breathing trial, and the tracheostomy cannula was removed on January 21, 2022. 
The patient was then transferred to the general ward on January 21, 2022 as her condition became stable On January 27, 2022, the administration of linezolid was suspended. TMP-SMX, voriconazole, and methylprednisolone were orally administered to the patient for anti-infection and anti-allergic vasculitis. On January 29, 2022, Nocardia farcinica and fungi were not discovered in her BALF. However, the cytomegalovirus antigen (PP65) was detected positive in blood. We then supplemented the treatment regimen with ganciclovir (500mg, orally tid) for anti-virus. She had no fever within one week (February 1-7, 2022), and her chest CT imaging signs were greatly recovered on February 6, 2022 (Figure 3C).
The patient was discharged on February 6, 2022. She continued taking TMP-SMX, ganciclovir, methylprednisolone, and voriconazole and had no obvious clinical symptoms including fever, cough, and seizure within the 2-month follow-up. The chest CT on April 16, 2022 showed several bronchial cavities in the lungs (Figure 3D). Her head MRI was gradually improving (Figure 4A and B). The treatment regimen was then changed to a combination of TMP-SMX and triamcinolone.