What are the differences between petechiae, purpura, and ecchymosis?

Differences Between Petechiae, Purpura, and Ecchymosis

Petechiae, purpura, and ecchymosis are distinct types of skin hemorrhages that differ primarily in size, with petechiae being the smallest (pinpoint), purpura being intermediate, and ecchymosis (bruising) being the largest form of cutaneous bleeding.

Key Differences

Size and Appearance

• Petechiae:

  • Pinpoint (<2 mm), round, flat red or purple spots
  • Do not blanch when pressure is applied
  • Appear as tiny dots on the skin surface
  • Often clustered together in specific areas

• Purpura:

  • Larger than petechiae (2-10 mm)
  • Flat, red or purple discolorations
  • Do not blanch with pressure
  • May be palpable (raised) in some conditions

• Ecchymosis:

  • Largest form (>10 mm, often several centimeters)
  • Commonly known as bruises
  • Initially appear red/purple then change color over time (blue, green, yellow)
  • Involve deeper layers of skin and subcutaneous tissue 1, 2

Depth of Involvement

• Petechiae: Superficial capillary bleeding
• Purpura: Involves dermal and sometimes subcutaneous vessels
• Ecchymosis: Deeper subcutaneous tissue extravasation of blood 3

Clinical Significance

Diagnostic Implications

• Petechiae:

  • Often indicate platelet disorders or capillary fragility
  • May be the first sign of serious conditions like meningococcemia or thrombocytopenia
  • Can appear in areas of increased pressure (after vomiting, coughing) 2

• Purpura:

  • Often associated with inflammatory or autoimmune conditions
  • May indicate vasculitis or coagulation disorders
  • Can be palpable (raised) in vasculitic conditions 4

• Ecchymosis:

  • May indicate trauma, anticoagulant use, or bleeding disorders
  • Larger size reflects greater blood extravasation
  • Can provide clues about timing of injury based on color changes 3

Distribution Patterns

• Petechiae on palms and soles: Classic for Rocky Mountain Spotted Fever 2
• Widespread petechiae with systemic toxicity: Concern for sepsis or necrotizing fasciitis 1
• Localized petechiae in infants: Often benign, possibly due to mechanical causes 5

Causes and Associations

Common Causes

1. Platelet disorders:

   • Decreased production (bone marrow disorders)
   • Increased destruction (ITP, TTP)
   • Dysfunction (medication-induced)

2. Vascular integrity issues:

   • Vasculitis
   • Vitamin C deficiency
   • Amyloidosis

3. Coagulation disorders:

   • Hemophilia
   • Von Willebrand disease
   • Factor XIII deficiency 2

4. Mechanical causes:

   • Increased pressure (vomiting, coughing, tourniquet effect)
   • Trauma 2, 5

5. Infectious causes:

   • Bacterial (meningococcemia, streptococcal infections)
   • Viral (enterovirus, EBV)
   • Rickettsial (Rocky Mountain Spotted Fever) 1, 2

Clinical Approach to Evaluation

When to Be Concerned

• Petechiae with fever: Requires urgent evaluation for sepsis 2
• Rapidly progressing rash: May indicate serious infection 2
• Widespread petechiae/purpura with systemic symptoms: Potential emergency 1
• Oral manifestations with spontaneous bleeding: Suggests significant coagulopathy 6

Diagnostic Workup

For significant or unexplained petechiae, purpura, or ecchymosis:

• Complete blood count with peripheral smear
• Coagulation profile (PT/INR, PTT)
• Inflammatory markers (CRP, ESR)
• Consider blood cultures if infection suspected 2

Special Considerations

In Children

• Well-appearing infants with localized petechiae/purpura without fever often have benign causes 5
• Petechiae in child abuse evaluations require investigation for underlying bleeding disorders 2

In Hematologic Disorders

• Essential thrombocythemia can present with various skin manifestations including petechiae, purpura, and ecchymosis in 22% of patients 7
• Autoimmune thrombocytopenic purpura may precede development of systemic lupus erythematosus 4

Understanding these differences is crucial for proper diagnosis and management of underlying conditions, particularly when these skin findings may represent the first sign of a serious systemic disorder.