What causes petechiae (small spots due to bleeding under the skin)?

Causes of Petechiae

Petechiae are most commonly caused by thrombocytopenia, coagulation disorders, vascular fragility, or infectious diseases, with the specific etiology requiring prompt evaluation based on clinical presentation and associated symptoms. 1

Primary Causes of Petechiae

Infectious Causes

• Bacterial infections:

  • Meningococcemia - rapidly progressing petechial rash with fever and systemic toxicity 2
  • Sepsis from various pathogens 1
  • Streptococcal infections - can cause petechiae in inflamed skin 2
  • Rocky Mountain Spotted Fever - classically presents with petechiae on palms and soles 2, 1
  • Ehrlichiosis and anaplasmosis - associated with leukopenia and thrombocytopenia 2

• Viral infections:

  • Enteroviral infections 2, 3
  • Parvovirus B19 4, 3
  • Epstein-Barr virus 2, 3
  • Cytomegalovirus 3
  • Respiratory viruses (influenza, parainfluenza, RSV, metapneumovirus) 3

Hematologic Disorders

• Platelet disorders:

  • Immune thrombocytopenia (ITP) 1
  • Thrombotic thrombocytopenic purpura (TTP) 1
  • Hemolytic uremic syndrome (HUS) 1
  • Disseminated intravascular coagulation (DIC) 1

• Coagulation disorders:

  • Von Willebrand disease 1
  • Hemophilia 1
  • Factor XIII deficiency 2

Vascular/Mechanical Causes

• Increased pressure:

  • Prolonged vomiting or coughing 2
  • Tourniquet-like phenomena (especially in infants) 5
  • Mechanical compression 6

• Vascular fragility:

  • Vasculitis 1
  • Connective tissue disorders 1
  • Vitamin C deficiency (scurvy) 1

Medication-Related

• Drug reactions:
  • Severe cutaneous adverse reactions 1
  • Anticoagulants and antiplatelet medications 1
  • Certain antibiotics and anticonvulsants 1

Clinical Evaluation Approach

History and Physical Examination Focus

• Distribution of petechiae (localized vs. generalized)
• Associated symptoms (fever, bleeding from other sites, joint pain)
• Recent infections or illnesses
• Medication history
• Family history of bleeding disorders 2

Key Laboratory Tests

1. First-line tests:

   • Complete blood count with peripheral blood smear
   • Coagulation profile (PT/INR, PTT)
   • Renal function tests
   • Liver function tests
   • Inflammatory markers (CRP, ESR) 1

2. Additional tests based on clinical suspicion:

   • Blood cultures (if infection suspected)
   • Specific testing for von Willebrand disease 1
   • ADAMTS13 activity (if TTP suspected)
   • PCR testing for tick-borne illnesses 2

Red Flags Requiring Urgent Evaluation

• Petechiae with fever (especially in children)
• Rapidly progressing rash
• Petechiae covering >30% body surface area
• Petechiae with altered mental status or hypotension
• Mucosal involvement or skin sloughing 1

Important Clinical Pearls

• Petechiae in well-appearing infants with localized distribution (especially lower limbs) and no fever often have benign causes 5
• Petechiae on the palms and soles are classically associated with Rocky Mountain Spotted Fever but can occur in other conditions 2, 1
• The presence of widespread petechiae with systemic toxicity should raise concern for necrotizing fasciitis rather than simple cellulitis 2
• In child abuse evaluations, the presence of petechiae requires investigation for underlying bleeding disorders unless there is clear evidence of abuse 2
• Viral infections are frequently associated with petechial rashes in children, with co-infections being common 3

Understanding the diverse causes of petechiae is essential for appropriate clinical management and to avoid unnecessary testing in benign conditions while ensuring prompt intervention in potentially life-threatening situations.