Differential Diagnosis for a 17-Month-Old Male with Recurrent Fevers

Single Most Likely Diagnosis

• Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Adenitis (PFAPA) Syndrome: This condition is characterized by recurrent fevers at regular intervals, often accompanied by other symptoms like aphthous stomatitis, pharyngitis, and adenitis. Although the question mentions fevers without symptoms, PFAPA syndrome is a common cause of periodic fever in children and should be considered, especially given the age of the patient and the regularity of the fevers.

Other Likely Diagnoses

• Familial Mediterranean Fever (FMF): An autosomal recessive disorder that causes recurrent episodes of fever, often accompanied by abdominal, chest, or joint pain. Elevated markers of inflammation like CRP and ferritin support this diagnosis.
• Hyper-IgD Syndrome (HIDS): Characterized by recurrent fevers, often with abdominal pain, rash, and joint pain. Although less common than PFAPA, it's a consideration in children with periodic fever and elevated inflammatory markers.
• Cyclic Neutropenia: A rare condition but can present with recurrent fevers due to neutropenia that occurs at regular intervals. However, the presence of elevated monocytes might not directly support this diagnosis unless there's a cyclic pattern to the neutropenia.

Do Not Miss Diagnoses

• Juvenile Idiopathic Arthritis (JIA): Particularly the systemic form, which can present with recurrent fevers, elevated inflammatory markers (like CRP and ferritin), and may not always have overt joint symptoms early in the disease course.
• Autoinflammatory Disorders (e.g., TNF Receptor-Associated Periodic Syndrome - TRAPS): These are critical to consider because they can have severe consequences if not treated properly. They often present with recurrent fevers and elevated inflammatory markers.
• Leukemia or Lymphoma: Although less likely, these conditions can cause recurrent fevers, elevated inflammatory markers, and abnormalities in blood cell counts. Given the potential severity, they must be ruled out.

Rare Diagnoses

• Chronic Granulomatous Disease (CGD): A disorder of phagocytic function that can lead to recurrent infections and inflammation, potentially causing periodic fevers.
• Muckle-Wells Syndrome: An autoinflammatory disorder that can present with recurrent fevers, rash, and joint pain, along with elevated inflammatory markers.
• Blau Syndrome: A rare genetic disorder characterized by the clinical triad of granulomatous dermatitis, symmetric arthritis, and recurrent uveitis, which can also include periodic fever.

Each of these diagnoses should be considered and investigated based on the clinical presentation, laboratory findings, and further diagnostic testing as necessary. The justification for each diagnosis is based on the combination of recurrent fevers, elevated inflammatory markers (CRP, ferritin, and monocytes), and the age of the patient.