Differential Diagnosis for Abnormal Bleeding in a Young Boy

The patient's laboratory results show decreased levels of Factors 9 and 2, with normal or near-normal levels of Factors 8 and 5. This pattern can help guide us toward the most likely cause of his abnormal bleeding.

• Single Most Likely Diagnosis

  • Vitamin K deficiency: This is the most likely diagnosis given the pattern of decreased Factor 9 and Factor 2 levels, with relatively spared Factor 8 and 5 levels. Vitamin K is essential for the gamma-carboxylation of Factors 2,7,9, and 10, and a deficiency can lead to decreased levels of these factors, resulting in a bleeding tendency. The fact that the boy is being treated with antibiotics, which can interfere with vitamin K production by gut flora, further supports this diagnosis.

• Other Likely Diagnoses

  • Hemophilia B: Although less likely given the pattern of factor deficiencies, hemophilia B (Factor 9 deficiency) could be considered if the decrease in Factor 9 was significantly more pronounced than the others. However, the concurrent decrease in Factor 2 levels points more towards a condition affecting multiple clotting factors, such as vitamin K deficiency.
  • Lupus anticoagulant: This condition can lead to an increased risk of thrombosis but can also cause a prolongation of clotting times in vitro due to its effect on phospholipid-dependent clotting tests. However, it would not typically cause the specific pattern of factor deficiencies seen here.

• Do Not Miss Diagnoses

  • Factor 2 deficiency: Although rare, a congenital deficiency of Factor 2 (prothrombin) could present with bleeding symptoms. The low level of Factor 2 in this patient could suggest this, but the concurrent decrease in other vitamin K-dependent factors makes vitamin K deficiency a more likely explanation.
  • Warfarin effect: If the patient had been exposed to warfarin (a vitamin K antagonist), this could lead to a similar pattern of clotting factor deficiencies. Although not directly mentioned, accidental ingestion or exposure should be considered and ruled out.

• Rare Diagnoses

  • Combined Factor deficiencies: Rare congenital conditions can lead to deficiencies of multiple clotting factors. While possible, these are less likely given the context (antibiotic treatment) and the specific pattern of deficiencies.
  • Liver disease: Severe liver disease can lead to decreased production of clotting factors. However, this would typically be associated with other signs of liver dysfunction and a more widespread decrease in clotting factor levels.