**Question:** A four year old boy was admitted with a history of abdominal pain and fever for two months, maculopapular rash for ten days, and dry cough, dyspnea and wheezing for three days. One examination liver and spleen were enlarged 4 cm and 3 cm respectively below the costal margins. His hemoglobin was 10.0 g/dl, platelet count 37 x 10^9/L and total leukocyte count 70 x 10^9/L, which included 80% eosinophils. Bone marrow examination revealed a cellular marrow comprising of 45% blasts and 34% eosinophils and eosinophilic precursors. The blasts stained negative for myeloperoxidase and non-specific esterase and were positive for CD19, CD10, CD22, and CD20. Which one of the following is the most likely diagnosis?

A. Acute leukemia
B. Chronic leukemia
C. Eosinophilic leukemia
D. Aplastic anemia

**Correct Answer:** D. Aplastic anemia

**Core Concept:** The provided information is indicative of a hematological disorder characterized by a deficiency in the production of mature blood cells. In this case, the presence of eosinophilia (80% eosinophils) and blasts (45%) in the bone marrow examination is a key feature that points towards a hematological disorder.

**Why the Correct Answer is Right:**

Eosinophilia is a sign of increased numbers of eosinophils, which are a type of white blood cell involved in immune response and tissue repair. In this scenario, the elevated eosinophil count (80%) indicates an increased production or activation of eosinophils as part of the patient's response to an underlying hematological disorder.

**Why Option D (Aplastic anemia) is Right:**

Aplastic anemia is a rare and severe bone marrow failure disorder characterized by a deficiency in the production of all three types of blood cells (red blood cells, white blood cells, and platelets). In this case, the patient exhibits symptoms of anemia (low hemoglobin) and thrombocytopenia (low platelet count), which are common presentations in aplastic anemia. Additionally, the bone marrow examination shows a low nucleated cell count (45% nucleated cells), indicating reduced hematopoiesis (blood cell production).

**Why Option C (Eosinophilic leukemia) is wrong:**

Leukemia is a group of cancers involving an abnormal proliferation of white blood cells. In this case, the patient does not have the typical symptoms and findings associated with leukemia, such as unexplained bleeding or infections, splenomegaly, and abnormal white blood cell count. Furthermore, the bone marrow examination shows a low nucleated cell count (45% nucleated cells), suggesting reduced hematopoiesis (blood cell production) rather than increased proliferation of white blood cells.

**Why Option A (Acute leukemia) is wrong:**

Acute leukemia is characterized by rapid proliferation of abnormal white blood cells, which is not consistent with the patient's clinical presentation. Additionally