A patient who is suspected of having acute viral hemorrhagic fever reveals history of tick bite. Which of the following is the most possible causative agent?

Correct Answer: C

Rationale: The correct answer is C: Crimean Congo virus. This is the most likely causative agent of acute viral hemorrhagic fever following a tick bite due to its association with tick transmission. Crimean Congo virus is a tick-borne virus that causes severe hemorrhagic fever in humans. The other options, Hantavirus, Rift Valley virus, and Marburg virus, are not typically transmitted by ticks. Hantavirus is spread through rodent feces, Rift Valley virus is transmitted by mosquitoes, and Marburg virus is transmitted through direct contact with infected animals or their bodily fluids. Therefore, based on the history of tick bite, Crimean Congo virus is the most probable causative agent.

Correct Answer: C

Rationale: The correct answer is C: Lymphocyte count. The International Prognostic Index (IPI) for non-Hodgkin's lymphoma includes factors such as age, number of extranodal sites, LDH level, performance status, and stage. Lymphocyte count is not a specific criteria in the IPI. This index is used to predict the outcome of patients with aggressive lymphomas. A higher score indicates a worse prognosis. A low lymphocyte count is not a consistent prognostic factor for non-Hodgkin's lymphoma, unlike the other factors listed. Therefore, choice C is not a criteria in the IPI, making it the correct answer.

Correct Answer: B

Rationale: The correct answer is B: Basophilic stippling. Basophilic stippling is a common finding in the peripheral blood smear of patients infected with hookworms due to lead poisoning, which can occur as a result of hookworm infection. Basophilic stippling is seen as the presence of small, dark blue granules within red blood cells and is indicative of impaired heme synthesis. Howell-Jolly bodies (A) are remnants of nuclear material in red blood cells and are typically seen in patients with functional asplenia. Target cells (C) are seen in conditions such as liver disease and hemoglobinopathies. Spherocytes (D) are seen in conditions like hereditary spherocytosis or autoimmune hemolytic anemia, but not specifically in hookworm infection.

Correct Answer: D

Rationale: The correct answer is D: Aplastic anemia. This condition is characterized by pancytopenia, which includes low hemoglobin (anemia), low platelets (manifested as petechiae), and low white blood cells (frequent infections). Dry tap marrow is a classic finding in aplastic anemia due to bone marrow failure. Iron deficiency anemia (choice A) typically presents with microcytic hypochromic anemia without pancytopenia. Megaloblastic anemia (choice B) is characterized by macrocytic anemia with hypersegmented neutrophils and is usually caused by deficiencies in vitamin B12 or folate. Hemolytic anemia (choice C) presents with anemia due to increased destruction of red blood cells, which does not explain the low platelets and white blood cells seen in this patient.

Correct Answer: C

Rationale: The correct answer is C: Microangiopathic hemolytic anemia. Schistocytes are fragmented red blood cells seen in conditions where RBCs are physically sheared or damaged as they pass through small blood vessels. In microangiopathic hemolytic anemia, abnormal or damaged blood vessels cause mechanical destruction of RBCs, leading to the formation of schistocytes. Sickle cell trait (A) and Thalassemia (B) are genetic disorders that do not typically cause schistocytes. Idiopathic thrombocytopenic purpura (D) is a condition characterized by low platelet count, not associated with schistocytes.