Differential Diagnosis for 28-month Female with Prolonged Fever and Leucocytosis

Single Most Likely Diagnosis

• Juvenile Idiopathic Arthritis (JIA): This condition is a common cause of prolonged fever in children, often accompanied by elevated white blood cell counts and neutrophilia. The age and presentation of the patient, along with the duration of fever, make JIA a strong consideration.

Other Likely Diagnoses

• Infectious Diseases (e.g., Tuberculosis, Osteomyelitis): Chronic infections can cause prolonged fever and elevated white blood cell counts. Neutrophilia suggests a possible bacterial infection.
• Lymphoma: Although less common, lymphoma can present with fever, leucocytosis, and neutrophilia, especially if there is involvement of the bone marrow.
• Autoimmune Neutropenia or other Autoimmune Disorders: Conditions like autoimmune neutropenia of infancy can sometimes present with neutrophilia due to a compensatory response, though this is less common.

Do Not Miss Diagnoses

• Leukemia (e.g., Acute Lymphoblastic Leukemia, Acute Myeloid Leukemia): These are critical diagnoses to consider due to their severity and the need for prompt treatment. Leukemia can present with fever, very high white blood cell counts, and neutrophilia, among other symptoms.
• Sepsis or Septicemia: Although the on-and-off nature of the fever might be less typical, sepsis is a life-threatening condition that requires immediate diagnosis and treatment.
• Endocarditis: Infective endocarditis can cause prolonged fever and elevated white blood cell counts. It's less common in this age group without a history of heart disease but is crucial not to miss.

Rare Diagnoses

• Chronic Granulomatous Disease (CGD): A rare genetic disorder that affects the immune system, leading to recurrent infections and could present with prolonged fever and leucocytosis.
• Hyper-IgE Syndrome (Job Syndrome): Characterized by recurrent cutaneous and pulmonary infections and elevated IgE levels. It could be considered in the differential for prolonged fever and elevated white blood cell counts, especially with a history of eczema or recurrent infections.
• Cyclic Neutropenia: A rare condition characterized by periodic episodes of neutropenia, which could potentially present with neutrophilia during the recovery phase, though this would be an unusual presentation for the condition.