Differential Diagnosis

The patient presents with a high white blood cell (WBC) count, elevated mean corpuscular volume (MCV), increased neutrophils, low red cell distribution width (RDW), and a swollen posterior auricle lymph node. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Chronic Myeloid Leukemia (CML): The elevated WBC count with a predominance of neutrophils and their precursors, along with a high MCV, could suggest CML, especially in the context of a swollen lymph node which might indicate lymphadenopathy associated with the disease.

• Other Likely Diagnoses

  • Infectious Mononucleosis: Caused by Epstein-Barr virus (EBV), it can present with lymphadenopathy, including posterior auricular nodes, and changes in blood cell counts, although the MCV might not be as significantly elevated.
  • Acute Bacterial Infections: Certain bacterial infections can cause a significant increase in WBC count, particularly neutrophils, and might also involve lymphadenopathy.
  • Chronic Lymphocytic Leukemia (CLL): Although CLL typically presents with lymphocytosis rather than neutrophilia, some cases can have a mixed picture, and lymphadenopathy is common.

• Do Not Miss Diagnoses

  • Acute Myeloid Leukemia (AML): AML can present with a high WBC count, abnormal neutrophil precursors, and lymphadenopathy. It's crucial to diagnose promptly due to its aggressive nature and need for immediate treatment.
  • Lymphoma: Both Hodgkin and non-Hodgkin lymphoma can cause lymphadenopathy and alterations in blood cell counts. The posterior auricular lymph node swelling could be a sign of lymphoma, making it a critical diagnosis not to miss.
  • Tuberculosis: Although less common in some regions, TB can cause lymphadenopathy and changes in blood cell counts. It's a diagnosis that should not be overlooked due to its public health implications and the need for specific treatment.

• Rare Diagnoses

  • Myeloproliferative Neoplasms (MPN) other than CML: Conditions like Polycythemia Vera, Essential Thrombocytosis, and Primary Myelofibrosis can sometimes present with elevated WBC counts and lymphadenopathy, though they are less common.
  • Hairy Cell Leukemia: A rare type of cancer that can cause lymphadenopathy and changes in blood cell counts, including an increase in WBC count.
  • Castleman Disease: A rare disorder that can cause lymphadenopathy and changes in blood cell counts, including an increase in WBC count, due to its impact on the immune system.

Each of these diagnoses requires careful consideration of the patient's full clinical picture, including additional laboratory tests and possibly imaging studies, to determine the most appropriate diagnosis and treatment plan.