An 18-year-old man with microcytic anemia, normal iron studies. Anemia?

Correct Answer: A

Rationale: The correct answer is A: Thalassemia. Thalassemia is a genetic disorder characterized by reduced production of hemoglobin, leading to microcytic anemia. Normal iron studies in this case suggest that iron deficiency anemia (choice B) is unlikely. Sideroblastic anemia (choice C) is characterized by abnormal iron utilization, not normal iron studies. Anemia of chronic disease (choice D) typically presents with normocytic or mildly microcytic anemia and is associated with underlying chronic inflammatory conditions. Therefore, given the clinical presentation of microcytic anemia with normal iron studies in an 18-year-old man, thalassemia is the most likely diagnosis.

Correct Answer: A

Rationale: The correct answer is A: Serum potassium 7.8 mEq/L. A high serum potassium level (hyperkalemia) can lead to life-threatening cardiac arrhythmias. Rapid action is necessary to prevent cardiac complications. Urine output slightly less than intake (choice B), oral mucosa inflammation (choice C), and ecchymoses on trunk (choice D) are important but do not require immediate action to prevent fatal consequences like hyperkalemia.

Correct Answer: C

Rationale: Correct Answer: C (Tissue factor) Rationale: 1. Tissue factor initiates the extrinsic pathway of the coagulation cascade by forming a complex with Factor VII. 2. This complex activates Factor X to Xa, leading to the common pathway of coagulation. 3. Factor XII is part of the intrinsic pathway and is not the primary initiator in vivo. 4. Thrombin is generated downstream in the cascade and amplifies coagulation but does not initiate it. 5. Factor X is activated further downstream in the common pathway and is not the primary initiator.

Correct Answer: C

Rationale: The correct answer is C: Diffuse large B-cell lymphoma. This is the most common type of lymphoma due to its aggressive nature and frequent occurrence in adults. It accounts for about 30% of all non-Hodgkin lymphomas. Hodgkin lymphoma (A) is less common and has distinct diagnostic features. Follicular lymphoma (B) is indolent and typically affects older adults. Mantle-cell lymphoma (D) is rarer and characterized by a specific genetic abnormality. Therefore, based on prevalence and characteristics, diffuse large B-cell lymphoma is the most common type.

Correct Answer: A

Rationale: The correct answer is A: Mature B cell immunophenotype. In ALL, a mature B cell immunophenotype is associated with a poorer prognosis because it indicates that the leukemia cells have progressed to a more advanced stage of differentiation, making them more aggressive and resistant to treatment. On the other hand, choices B, C, and D are good prognostic factors in ALL. Female gender is associated with a better response to treatment, hyperploidy is a favorable genetic feature, and age 4-10 years is a common age group with a higher likelihood of responding well to treatment.