Differential Diagnosis

The patient presents with sudden onset of thrombocytopenia (platelets at 65) and an elevated INR (1.9), indicating a coagulopathy. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Viral Hepatitis or Liver Injury: The combination of thrombocytopenia and an elevated INR suggests liver dysfunction, as the liver produces clotting factors. Viral hepatitis or a liver injury could lead to these lab findings due to the liver's compromised ability to produce these factors and possibly due to a consumptive coagulopathy.

• Other Likely Diagnoses

  • Disseminated Intravascular Coagulation (DIC): This condition involves both clotting and bleeding as it consumes platelets and clotting factors, leading to thrombocytopenia and elevated INR. It can be triggered by various conditions, including infections, trauma, and malignancies.
  • Vitamin K Deficiency: Deficiency in vitamin K can lead to an elevated INR because vitamin K is essential for the production of clotting factors in the liver. However, it might not directly cause thrombocytopenia unless it's part of a broader malabsorptive syndrome.
  • Medication-Induced Coagulopathy: Certain medications, such as warfarin, can cause an elevated INR. If the patient is on such medications, this could be a contributing factor, though thrombocytopenia would be less directly related unless the medication also affects platelet production or function.

• Do Not Miss Diagnoses

  • Hemolytic Uremic Syndrome (HUS) or Thrombotic Thrombocytopenic Purpura (TTP): Although these conditions primarily present with thrombocytopenia and microangiopathic hemolytic anemia, they can have a wide range of presentations. Missing these diagnoses could be fatal, so they must be considered, especially if there are additional symptoms like renal failure or neurological abnormalities.
  • Sepsis: Sepsis can lead to DIC, which would explain the lab findings. It's crucial not to miss sepsis due to its high mortality rate if not promptly treated.

• Rare Diagnoses

  • Thrombocytopenia with Absent Radius (TAR) Syndrome: This is a rare genetic disorder characterized by thrombocytopenia and bilateral absence of the radius. However, it's congenital and wouldn't typically present with sudden onset in adulthood.
  • Glanzmann's Thrombasthenia: A rare bleeding disorder characterized by a platelet dysfunction. While it could potentially lead to bleeding complications, it doesn't directly explain the elevated INR unless there's a concurrent condition affecting liver function or clotting factor production.
  • Congenital Coagulopathies (e.g., Hemophilia): These conditions are typically diagnosed in childhood but could be considered if there's a new presentation or a previously undiagnosed mild form. However, they wouldn't typically cause sudden thrombocytopenia unless there's an acute hemorrhage or other complicating factor.