A 24-year-old White man presented with 1-day complaints of progressive shortness of breath and fever. He recently underwent an open reduction and internal fixation of a left midshaft femur fracture from a skiing accident 4 days ago. He denied chest pain, skin rashes, hemoptysis, hematemesis, melena, or surgical site bleeding. On arrival, the patient appeared in mild respiratory distress with a respiratory rate of 23 breaths/min, temperature of 37.8°C, heart rate of 97 beats/min, BP of 95/54 mm Hg, and peripheral saturation of 97% on 6-L/min nasal canula. His initial peripheral saturation on room air was 67%. Physical examination was unremarkable, except for diffuse rhonchi on chest auscultation. Chest radiograph on admission showed alveolar opacities predominantly in bilateral lower lobes. A chest CT angiography revealed no evidence for pulmonary embolism. However, there were findings of diffuse bilateral ground-glass opacities with areas of patchy consolidation and innumerous micronodules in both lungs (Fig 1). Laboratory examination was significant for a drop of hemoglobin by 3 g/dL and hematocrit level by 7% since his hospital discharge 4 days earlier. His renal function and urine analysis were normal. Venous blood gas on admission showed pH of 7.39 and Pco2 of 43 mm Hg. Because of unexplained acute anemia, nonspecific CT chest findings and progressive dyspnea, a bronchoscopy with BAL was performed. Four aliquots of 60 mL saline solution were injected for lavage with fluid return (Fig 2). BAL fluid showed WBC count of 0.411 × 103/mm3, RBC count of 318 × 103/mm3, 100% fresh RBCs, 73% neutrophil, 24% lymphocytes, 1% monocytes, and 2% eosinophils. BAL fluid cytologic condition is shown in Figure 3. A full vasculitis workup by rheumatology was unremarkable. Ophthalmologic and skin examination were unrevealing.

A 70-year-old woman who had received a diagnosis of pneumonia in the right lower lobe was treated with antibiotics at a general practitioner's clinic 9 months earlier. Her pneumonia had improved, but the cough and lung infiltrates persisted for > 6 months, so the patient was referred to our hospital. She had undergone surgery for breast cancer 30 years earlier but had no other medical history. She was not taking any medications and had no history of smoking, including passive smoking.

A 58-year-old man presented to us with a 1-week history of high-grade fever and progressive dry cough. Four weeks before his presentation, he was diagnosed with COVID-19 infection and needed non-ICU hospital admission with no supplemental oxygen requirements for 6 days and was treated with a 5-day course of remdesivir and 3 weeks of dexamethasone. His steroid dose was commenced on dexamethasone 12 mg bid (four times the recommended dose) for 14 days and then gradually tapered over the remaining 7 days. His history was unremarkable, except for well-controlled asthma. He did not complain of any shortness of breath, weight loss, or loss of appetite. He was never a smoker and denied any alcohol use.

A 31-year-old man with a medical history of well-controlled asthma presented with a 3-week history of midsternal chest pressure and shortness of breath. His symptoms were associated with malaise, weakness, 40-pound weight loss over several months, and intermittent fever up to 38.3ºC. A week and half earlier, he started experiencing a productive cough with white sputum and arthralgias in his knees. He denied any exacerbating or relieving factors for his symptoms. Additionally, he had a pruritic rash on his thighs for the last year that remained unresolved despite antifungal medication.

A 73-year-old frail woman presented with 3 months of progressively worsening exertional dyspnea, mild cough with white mucus, voice changes, and few episodes of dysphagia. She denied weight loss, night sweats, chest pain, or hemoptysis. Medical history was significant for hypertension, remote 30 years of tobacco use, and regular alcohol use. She had neither asbestos nor occupational exposure. She had no family history of malignancy.

In an asymptomatic 19-year-old who regularly underwent cardiopulmonary fitness testing for national lifeguard-accreditation, 129Xe MRI unexpectedly revealed an abnormally augmented RBC signal and RBC-to-alveolar-capillary-tissue ratio with spatially homogeneous ventilation, tissue barrier, and RBC images. Pulmonary function was normal, but cardiopulmonary follow-up including transthoracic and transesophageal echocardiogram, heart catheterization, and contrast-enhanced cardiac CT imaging led to the diagnosis of a large (20 × 27 mm) secundum atrial septal defect (ASD) with a net right-to-left shunt (Qp:Qs = 0.5) and normal pulmonary pressures. This novel, unexpected case revealed that 129Xe RBC signal intensity likely reflected erythrocytosis, compensatory to the abnormal cardiovascular hemodynamics that resulted from a large congenital ASD. Unlike ASD cases that present with dyspnea and exercise limitation, this 129Xe MRI abnormality was detected in an asymptomatic teenager. This is the first report of asymptomatic adult congenital heart disease diagnosed subsequent to novel 129Xe MRI that led to early intervention, avoiding long-term complications of cyanosis, including ventricular fibrosis and thromboembolic and bleeding risks.