Differential Diagnosis for an 8-year-old Female with Fatigue, Pallor, and Unexplained Bruises

Single Most Likely Diagnosis

• C. AML (Acute Myeloid Leukemia): The presence of Auer rods in many of the blast cells is highly suggestive of AML. Auer rods are abnormal azurophilic granules found in the cytoplasm of myeloid blast cells and are characteristic of AML. The manual differential showing 53% blasts with a significant proportion of myeloid lineage cells (promyelocytes, myelocytes, metamyelocytes) and the marked decrease in platelets also support this diagnosis.

Other Likely Diagnoses

• A. ALL (Acute Lymphoblastic Leukemia): Although the presence of Auer rods points more towards AML, ALL is a common cause of fatigue, pallor, and bruising in children due to bone marrow infiltration by lymphoblasts. However, the specific findings of Auer rods and the differential count provided make ALL less likely.
• B. CML (Chronic Myeloid Leukemia): CML is rare in children and typically presents in a chronic phase with much higher leukocyte counts and a different differential count, with more mature myeloid cells. The presence of 53% blasts is not consistent with the typical presentation of CML.

Do Not Miss Diagnoses

• Infection or Sepsis: Although the laboratory findings point towards a hematological malignancy, infection or sepsis can cause significant alterations in the CBC, including a high WBC count with a left shift (presence of immature cells) and thrombocytopenia. These conditions are medical emergencies and must be considered, especially if the patient shows signs of infection or sepsis.
• Bone Marrow Failure Syndrome: Conditions like aplastic anemia or other bone marrow failure syndromes can present with pancytopenia (decreases in all blood cell lines) and might be considered, especially if there's a history suggestive of exposure to toxins, medications, or a family history of such conditions.

Rare Diagnoses

• Burkitt Lymphoma (D): While Burkitt lymphoma can cause bone marrow involvement and alterations in the CBC, it typically presents with a more specific clinical picture, including rapidly enlarging masses, often in the abdomen, and distinct cytogenetic abnormalities (e.g., t(8;14)). The presence of Auer rods and the specific differential count provided make this diagnosis less likely.
• Other Myeloproliferative Neoplasms: Rare conditions like juvenile myelomonocytic leukemia (JMML) or other myeloproliferative neoplasms could be considered but are less likely given the specific findings of Auer rods and the high percentage of blasts, which are more characteristic of AML.