Differential Diagnosis for Bilateral Petechiae of Calves

• Single most likely diagnosis
  • Idiopathic Thrombocytopenic Purpura (ITP): This condition is characterized by low platelet count, leading to petechiae, and can present with bilateral calf petechiae due to increased venous pressure and platelet consumption.
• Other Likely diagnoses
  • Vasculitis: Conditions like leukocytoclastic vasculitis can cause petechiae on the lower extremities, including the calves, due to inflammation of small blood vessels.
  • Scurvy: Vitamin C deficiency can lead to blood vessel fragility, resulting in petechiae, and is more likely to be seen in malnourished individuals or those with poor dietary habits.
  • Henoch-Schönlein Purpura (HSP): Although more common in children, HSP can cause petechiae, typically on the lower extremities, along with other symptoms like abdominal pain and arthritis.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Disseminated Intravascular Coagulation (DIC): A serious disorder that can cause both thrombosis and bleeding, including petechiae, due to consumption of clotting factors and platelets. It requires immediate attention.
  • Meningococcemia: A severe infection caused by Neisseria meningitidis, which can present with petechiae or purpura, and is a medical emergency due to its high mortality rate if not promptly treated.
  • Thrombotic Thrombocytopenic Purpura (TTP): A rare blood disorder characterized by the formation of blood clots in small blood vessels throughout the body, which can lead to petechiae among other symptoms, and is life-threatening if not treated.
• Rare diagnoses
  • Ehlers-Danlos Syndrome: A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues, which can lead to easy bruising and petechiae due to fragile blood vessels.
  • Amyloidosis: A condition characterized by the deposition of amyloid (a particular type of protein) in various tissues of the body, which can cause blood vessel fragility and lead to petechiae, among other symptoms.