Differential Diagnosis for a 14-year-old boy with fever, headache, anorexia, body ache, thrombocytopenia, and anemia

• Single most likely diagnosis:
  • Dengue fever: Justification - The symptoms of fever, headache, anorexia, body ache, and significantly, thrombocytopenia (low platelet count of 80,000) along with a PCV (Packed Cell Volume) of 35, which might indicate some degree of anemia or hemoconcentration, are classic for dengue fever, especially in endemic areas.
• Other Likely diagnoses:
  • Viral infections (e.g., influenza, enterovirus): Justification - These can cause similar symptoms of fever, headache, and body aches, though thrombocytopenia is less common.
  • Malaria: Justification - Although more commonly associated with cyclic fevers and specific travel or exposure history, malaria can cause anemia, thrombocytopenia, and similar symptoms.
  • Typhoid fever: Justification - Can present with fever, headache, and body aches, and while less commonly associated with significant thrombocytopenia, it's a consideration in certain geographic areas.
• Do Not Miss diagnoses:
  • Meningitis: Justification - Although the primary symptoms don't directly point towards meningitis, the presence of fever and headache necessitates consideration of this potentially life-threatening condition, especially if there are signs of neck stiffness or altered mental status.
  • Sepsis: Justification - Any patient with fever, especially when combined with other systemic symptoms, should be evaluated for sepsis, a life-threatening condition that requires immediate intervention.
  • Hemorrhagic fever (e.g., Ebola, Lassa fever): Justification - In specific geographic or exposure contexts, these diseases can present with similar symptoms and are critical to identify due to their high mortality and public health implications.
• Rare diagnoses:
  • Thrombotic thrombocytopenic purpura (TTP): Justification - A rare blood disorder characterized by thrombocytopenia, microangiopathic hemolytic anemia, and renal and neurological abnormalities, which could explain some of the patient's symptoms.
  • Hemophagocytic lymphohistiocytosis (HLH): Justification - A rare disorder of the immune system that can cause fever, cytopenias (including thrombocytopenia), and other systemic symptoms, often requiring specific diagnostic tests for identification.
  • Leptospirosis: Justification - Can cause a wide range of symptoms including fever, headache, and body aches, and in severe cases, can lead to thrombocytopenia and other complications, particularly in individuals with specific occupational or recreational exposures.