An 18-year-old female patient presented to the emergency department with complaints of high fever (40.2°C), chills, and sore throat. She also had chest pain, dyspnea, and tachypnea (respiratory rate:30 breaths/min; 80% oxygen saturation). Physical examination revealed edematous and congested oropharyngeal mucosa, along with acute tonsillitis and right-sided neck edema. Laboratory tests revealed leukocytosis (leukocyte count, 18,000/mm3 ) and elevated levels of C-reactive protein (26.3 mg/L). Blood culture was positive for anaerobic Fusobacterium necrophorum.

A 66-year-old woman presented with an approximately 15-day history of headache and no associated symptoms. Her complete blood counts were normal, and blood and urine cultures were negative. Brain magnetic resonance imaging showed multiple lesions in the bilateral temporal and right frontal lobes with T2 hyperintensity, restricted diffusibility, and peripheral enhancement, suggesting abscesses (Figure 1A–C). Porphyromonas gingivalis was confirmed as the etiological agent via biopsy. Subsequently, the family members reported that the patient had undergone a dental procedure 1 month before symptom onset. Because of a delayed surgical approach, the lesions progressed and the patient developed an ischemic vascular insult in the territory of the middle cerebral arteries (Figure 1D), probably related to vasculitis secondary to the adjacent inflammatory/infectious process.

A 26-year-old man was admitted with fever and headache that persisted for 2 weeks, progressing with reduced consciousness and seizures. Serological tests for HIV showed positive results and the CD4 count was 76 cells/mm3 . The serological test for syphilis showed negative results. Cerebrospinal fluid analysis revealed pleocytosis (42/mm³) with lymphocytic predominance, increased protein concentration (125 mg/mL), a negative VDRL test result, and a positive cryptococcal capsular polysaccharide antigen test result with fungal culture positive for Cryptococcus neoformans. Brain magnetic resonance imaging showed multiple intra-axial lesions scattered throughout the cerebral hemispheres (Figure A and Figure B) without significant enhancement with gadolinium (Figure C), suggesting perivascular impairment due to gelatinous pseudocysts. Treatment with intravenous amphotericin B deoxycholate 0.7 mg/kg/d and flucytosine 100 mg/kg/d was initiated, but the patient died 1 week later.

A 78-year-old man presented to the emergency department with a seven-day history of headache, fever, diffuse myalgias, dry cough, and dyspnea. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was diagnosed by SARS-CoV-2 RNA detection in nasopharyngeal samples. Chest computed tomography (CT) demonstrated predominantly peripheral ground-glass opacities in both lungs (Figure 1A), suggestive of a viral infection. The patient’s cough markedly worsened during hospitalization. He experienced sudden onset anterior chest pain radiating to the neck, followed by dyspnea, after a severe coughing episode. The patient’s peripheral oxygen saturation on room air was 88%. Repeat CT showed extensive subcutaneous emphysema dissecting the muscular planes of the cervical and dorsal regions, extending into the mediastinum and medullary canal (Figures 1B-D). He was treated with analgesics, cough suppressants, and supplemental oxygen through a nasal cannula, showing partial improvement.

A 20-year-old man was admitted to the hospital due to hypotonia, dystonic movements, and dysarthria. The patient’s symptoms began and had been progressing since the age of 5, when he experienced an episode of enteroviral encephalitis. The patient’s family history included no relevant information. His blood count, biochemistry, and cerebrospinal fluid at the time of admission were unremarkable. Laboratory investigation yielded negative findings for Huntington’s disease, neuroacanthocytosis, Wilson’s disease, and mitochondrial encephalopathies. Brain magnetic resonance imaging showed bilateral volume loss, and high signal intensity of the caudate nuclei and putamina on a fluid attenuation inversion recovery sequence, with no enhancement after contrast injection (Figure 1). Given his clinical history of viral encephalitis associated with progressive neurological symptoms and imaging findings, enterovirus-associated bilateral striatal necrosis (BSN) was the most likely diagnosis.

A 58-year-old man was admitted to the emergency department with a three-day history of fever, cough, and dyspnea. At admission, he was tachypneic (respiratory rate of 30 breaths/min), his body temperature was 38.2ºC, and his oxygen saturation was 89%. Laboratory fi ndings were unremarkable. Chest computed tomography showed multiple areas of groundglass opacity in both lungs, suggestive of viral infection, and treein-bud opacities with bronchial wall thickening and small nodules, suggestive of pulmonary tuberculosis (TB; Figure 1). The patient was diagnosed as having COVID-19 by real-time polymerase chain reaction. The diagnosis of TB was confi rmed by culture.