Petichial Rash – Causes

A non-blanching petechial rash (i.e., small red or purple spots on the skin that don’t disappear when pressure is applied) is a concern because it might indicate a serious underlying condition. The differential diagnosis (DDx) for a non-blanching petechial rash includes:

  1. Infectious Causes:
    • Meningococcal septicemia/meningitis: Caused by Neisseria meningitidis, this can progress rapidly and be fatal.
    • Other bacterial sepsis: Such as those caused by Streptococcus pneumoniae or Haemophilus influenzae.
    • Viral infections: Many viral infections can lead to petechiae including enteroviruses, EBV, CMV, and some arboviruses.
    • Rickettsial infections: E.g., Rocky Mountain spotted fever.
    • Endocarditis: Infection of the heart valves can lead to emboli which can cause petechiae.
  2. Hematologic Causes:
    • Idiopathic thrombocytopenic purpura (ITP): An autoimmune disease leading to platelet destruction. Often post infection.
    • Thrombotic thrombocytopenic purpura (TTP): A disorder causing clotting in small blood vessels. Usually ADAMTS13 deficiency.
    • Hemolytic uremic syndrome (HUS): Typically seen in children after a diarrheal illness caused by certain strains of E. coli.
    • Leukemia or other malignancies: Can lead to bone marrow suppression and thrombocytopenia.
    • Von Willebrand disease and other clotting disorders.
    • Disseminated intravascular coagulation (DIC): A widespread activation of the clotting cascade.
  3. Drug-Related:
    • Drug-induced thrombocytopenia: Some drugs (ie heparin) can lead to decreased platelet counts. HIT (Heparin Induced Thrombocytopaenia).
    • Anticoagulant therapy: Excessive anticoagulation can cause bleeding.
  4. Vascular Causes:
    • Vasculitis: Inflammation of blood vessels can cause petechiae.
    • Henoch-Schönlein purpura (HSP): A type of vasculitis seen in children (usually post viral)
  5. Trauma or Physical Causes:
    • Tourniquet test or tight bandages: Can cause petechiae under the area of compression.
    • Child abuse: Especially in the context of shaken baby syndrome.
    • Pressure changes: Such as those experienced by divers or after vigorous coughing (also known as purpura due to coughing).
  6. Rare Causes:
    • Ehlers-Danlos syndrome: A connective tissue disorder that can make the skin more fragile.
    • Scurvy: Due to vitamin C deficiency.