Differential Diagnosis for Elevated WBC and Platelet Count

Single Most Likely Diagnosis

• Essential Thrombocythemia: This is a myeloproliferative neoplasm characterized by an elevated platelet count, often accompanied by an increase in white blood cell count. The chronic nature of the elevation (5 years) and the combination of elevated WBC and platelets make this a strong consideration.

Other Likely Diagnoses

• Chronic Myeloid Leukemia (CML): CML can present with an elevated WBC count and sometimes an increased platelet count. The long duration of symptoms could fit with the chronic phase of CML.
• Polycythemia Vera: Another myeloproliferative neoplasm that can cause an increase in all three blood cell lines (erythrocytosis, leukocytosis, and thrombocytosis), although erythrocytosis is more characteristic.
• Reactive Leukocytosis with Secondary Thrombocytosis: Chronic infection, inflammation, or another reactive cause could lead to a sustained elevation in WBC, with a secondary increase in platelets due to the body's response to inflammation.

Do Not Miss Diagnoses

• Chronic Myelomonocytic Leukemia (CMML): A type of leukemia that can present with an elevated WBC count and sometimes thrombocytosis. It's crucial to diagnose due to its potential for progression and the need for specific management.
• Myeloproliferative Neoplasm, Unclassifiable: In cases where the specific type of myeloproliferative neoplasm cannot be determined, this diagnosis is considered. It's essential not to miss this due to the implications for treatment and prognosis.
• Leukemia (Acute or Other Types): Although less likely given the chronic nature, acute leukemias or other types (like acute lymphoblastic leukemia) can present with elevated WBC counts and require urgent diagnosis and treatment.

Rare Diagnoses

• Primary Myelofibrosis: A myeloproliferative neoplasm characterized by fibrosis of the bone marrow, which can lead to elevations in WBC and platelet counts, although it more commonly presents with cytopenias.
• Mastocytosis: A condition involving the accumulation of mast cells in one or more organs, which can rarely cause an elevated WBC count and thrombocytosis.
• Other Rare Myeloproliferative Neoplasms: Such as atypical CML, juvenile myelomonocytic leukemia (in younger patients), or unclassified myeloproliferative disorders.