Can Contusion Occur Without Trauma?
Yes, contusions can occur without obvious external trauma, particularly in patients with underlying bleeding disorders, though this is uncommon and requires systematic evaluation to distinguish from occult trauma.
Clinical Context and Mechanism
While contusions typically result from direct blunt force trauma 1, certain medical conditions can produce bruising patterns that appear spontaneous or occur from minimal trauma that would not normally cause bruising in healthy individuals.
When to Suspect "Traumaless" Contusion
Bleeding Disorders as Primary Cause
In patients presenting with unexplained bruising, bleeding disorders must be systematically evaluated, as they can cause contusions from minimal or unrecognized trauma 2:
- Von Willebrand disease (most common inherited bleeding disorder, prevalence ~1 in 1000) presents with easy bruising and mucocutaneous bleeding 3
- Hemophilia (Factor VIII or IX deficiency) can cause significant bruising even with mild deficiencies, particularly after minimal trauma 2
- Factor XIII deficiency causes bruising but is not detected by standard PT/aPTT screening 3
- Platelet function disorders present with bruising and require specialized testing 2, 3
- Immune thrombocytopenia (ITP) characterized by low platelet count can cause spontaneous bruising 3
Other Medical Conditions
Additional causes of apparent "spontaneous" bruising include 2, 3:
- Vascular disorders: Ehlers-Danlos syndrome, arteriovenous malformations, senile purpura
- Nutritional deficiencies: Vitamin K deficiency (especially in infants without prophylaxis), scurvy
- Systemic diseases: Liver disease/cirrhosis, disseminated intravascular coagulation (DIC), malignancies
- Medications: Anticoagulants, antiplatelets, NSAIDs, steroids, certain antibiotics
Critical Distinction: Occult vs. Truly Spontaneous
In Pediatric Populations
In nonmobile infants, bleeding disorders can present with bruising at sites of normal handling or pressure, which may appear "traumaless" but actually results from minor trauma that would not affect normal children 2:
- Petechiae at clothing line pressure sites
- Bruising at sites of object pressure (e.g., infant seat fasteners)
- Bruising from routine handling
Hidden Trauma Scenarios
Contusions can occur without visible external trauma in specific circumstances 4:
- Internal organ contusion (e.g., cardiac contusion) can occur from blunt chest trauma without external signs 4
- Acceleration-deceleration injuries can cause brain contusions without obvious external head trauma 5
Diagnostic Algorithm
Initial Evaluation
When confronted with unexplained bruising 2, 3:
- Complete blood count with platelet count to evaluate for thrombocytopenia 3
- PT and aPTT to detect most factor deficiencies (but not VWD or Factor XIII) 2, 3
- Fibrinogen concentration and thrombin time for fibrinogen defects 2, 3
When Standard Tests Are Normal
If PT/aPTT are normal but clinical suspicion remains high, additional testing is mandatory 3:
- Von Willebrand disease testing (not detected by PT/aPTT)
- Factor XIII assay
- Platelet function testing (PFA-100 or platelet aggregation studies)
Common Pitfalls to Avoid
- Do not assume normal PT/aPTT rules out bleeding disorders, as these tests miss VWD, Factor XIII deficiency, and platelet function disorders 3
- In children with unexplained bruising, evaluation for bleeding disorders should occur simultaneously with evaluation for abuse 2
- Mild hemophilia can cause significant bleeding even with normal aPTT 2
- In nonmobile infants, bruising from normal handling suggests bleeding disorder rather than abuse 2
When Bleeding Disorder Evaluation Is NOT Required
The American Academy of Pediatrics specifies that bleeding disorder evaluation can be excluded when 2:
- Caregivers' description of trauma sufficiently explains the bruising
- Independent witness provides history of trauma explaining the bruising
- Abusive object or hand-patterned bruising is present (indicating trauma occurred)