A patient with a severe viral infection exhibits reduced levels of circulating lymphocytes. Which of the following mechanisms is most likely responsible for this observation?

Correct Answer: A

Rationale: A patient with a severe viral infection exhibiting reduced levels of circulating lymphocytes is likely due to the apoptosis of infected lymphocytes. When a virus enters the body, it can infect and replicate within lymphocytes, subsequently triggering the immune system to induce apoptosis in infected cells to prevent further spread of the virus. This process is part of the body's defense mechanism to control the viral infection. As a result, the circulating lymphocyte levels may decrease as infected lymphocytes are targeted for apoptosis. This phenomenon helps to limit viral replication and spread within the body, thereby aiding in the immune response to eliminate the virus.

Correct Answer: C

Rationale: In a patient with ARDS who is experiencing refractory hypoxemia despite maximal ventilatory support and prone positioning, the use of extracorporeal membrane oxygenation (ECMO) is a potentially life-saving adjunctive therapy. ECMO works by providing temporary support for gas exchange outside the body, allowing the lungs to rest and heal while providing adequate oxygenation and carbon dioxide removal. The use of ECMO has been associated with improved oxygenation and reduced mortality in severe cases of ARDS, especially in patients who fail conventional therapies. High-frequency oscillatory ventilation (HFOV) has not consistently shown mortality benefit in ARDS, continuous renal replacement therapy (CRRT) is not directly indicated for hypoxemia in ARDS, and inhaled nitric oxide (iNO) has shown limited benefit in improving oxygenation in ARDS without a clear impact on mortality.

Correct Answer: A

Rationale: Acute respiratory distress syndrome (ARDS) is a serious and life-threatening condition characterized by rapid onset of respiratory failure, severe hypoxemia (low oxygen levels in the blood), and non-cardiogenic pulmonary edema. The hallmark of ARDS is severe hypoxemia that is difficult to correct even with high levels of supplemental oxygen. Patients with ARDS often require mechanical ventilation to maintain adequate oxygen levels. Severe cough with purulent sputum production, chest pain exacerbated by deep breathing, and productive cough with hemoptysis are not typical features of ARDS.

Correct Answer: B

Rationale: Disseminated intravascular coagulation (DIC) is a condition characterized by widespread activation of coagulation leading to both thrombosis and hemorrhage. In patients with chronic liver disease, especially in the setting of advanced cirrhosis, DIC can develop due to factors such as decreased synthesis of coagulation factors and impaired clearance of activated clotting factors. The patient in this scenario presents with signs of both abnormal bleeding (bruising, petechiae, mucosal bleeding) and laboratory findings consistent with DIC, including prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT) along with decreased platelet count.

Correct Answer: B

Rationale: The patient's presentation of severe headache, blurred vision, and fatigue, along with the laboratory findings of elevated white blood cell count, thrombocytosis, and JAK2 V617F mutation, are characteristic of essential thrombocythemia. This is a myeloproliferative neoplasm characterized by the clonal proliferation of megakaryocytes, leading to an increased platelet count. The JAK2 V617F mutation is commonly found in essential thrombocythemia and other myeloproliferative disorders. The symptoms of essential thrombocythemia can be related to the increased blood viscosity and risk of thrombosis due to the elevated platelet count. Polycythemia vera would present with elevated red blood cell count, hemoglobin, and hematocrit, along with other features such as pruritus after a hot bath. Chronic myeloid leukemia (CML