What causes multiple small bruises on the legs and how are they treated?

Multiple Small Bruises on the Legs: Causes and Management

The approach to multiple small bruises on the legs depends critically on patient age, bruise location, and associated symptoms—with immediate laboratory evaluation required if there are concerning features such as spontaneous bleeding, mucosal bleeding, or bruising in unusual locations.

Age-Specific Considerations

In Young Children (< 24 months)

• Bruising in infants < 6 months old is highly concerning and warrants immediate evaluation for abuse, regardless of location or explanation provided 1
• For children 6-12 months old, bruising on the legs (particularly upper legs) requires skeletal survey if there is no adequate history of accidental trauma 1
• In children 12-24 months old, bruising on bony prominences (like shins) with a plausible trauma history is typically benign, but bruising on the upper leg, foot, or other unusual locations requires further evaluation 1
• Any patterned bruising, multiple bruises, or bruising with additional injuries (burns, whip marks) necessitates immediate evaluation for abuse regardless of age 1

In Adults and Older Children

• Accidental bruises in adults occur predictably on extremities (nearly 90% of cases), particularly the legs, and are usually related to known minor trauma 2
• Bruising on unusual locations (neck, ears, genitalia, buttocks, trunk) should raise concern for underlying pathology or non-accidental injury 2

Medical Causes Requiring Evaluation

Bleeding Disorders

• Von Willebrand disease is the most common inherited bleeding disorder (1 in 1000 people) and presents with easy bruising and mucocutaneous bleeding 3
• Hemophilia (Factor VIII or IX deficiency) can cause significant bruising even with mild deficiencies 3
• Immune thrombocytopenia (ITP) presents with low platelet counts and spontaneous bruising 3
• Platelet function disorders can cause bruising despite normal platelet counts and require specialized testing like platelet aggregation studies 3

When to Suspect Medical Causes

Evaluate for bleeding disorders when 1:

• History of excessive bleeding after circumcision, surgery, or dental procedures
• Epistaxis or bleeding from umbilical stump
• Family history of bleeding disorders
• Bruising accompanied by mucosal bleeding (gums, nosebleeds)
• Medications affecting coagulation (anticoagulants, NSAIDs, steroids, certain antibiotics) 3

Other Medical Conditions

• Ehlers-Danlos syndrome causes easy bruising due to capillary and perivascular connective tissue fragility, with the vascular subtype being particularly dangerous 4
• Vitamin K deficiency (especially in infants without prophylaxis at birth) 3
• Liver disease/cirrhosis causing decreased clotting factor production 3
• Malignancies and infiltrative disorders 1, 3

Diagnostic Approach

Initial Laboratory Testing

When bleeding disorder is suspected, obtain 1, 3:

• Complete blood count with platelet count (to detect thrombocytopenia)
• Prothrombin time (PT) and activated partial thromboplastin time (aPTT)
• Note: PT/aPTT do not detect von Willebrand disease, Factor XIII deficiency, or platelet function disorders 3
• Fibrinogen level (to detect fibrinogen defects) 3

When Laboratory Evaluation is NOT Needed

Skip extensive bleeding disorder workup when 1:

• Caregivers provide adequate explanation for trauma
• Child or independent witness describes accidental or abusive trauma
• Patterned bruising with clear history of being struck
• Bruising location and pattern consistent with normal childhood activity in mobile children

Treatment

Acute Management of Traumatic Bruising

• Apply local cold, compression, and elevation of the injured part immediately 5
• Rest and restrict activity to prevent extension of injury 6
• Protect from further injury during healing 6
• Lack of treatment may lead to complications such as muscle shortening 5

Special Populations

Chemotherapy Patients

• Thrombocytopenia is the most likely cause and requires immediate laboratory confirmation 7
• Hold all anticoagulation including prophylactic LMWH 7
• Administer platelet transfusions to maintain counts >20 × 10⁹/L prophylactically or >50 × 10⁹/L if active bleeding 7
• Avoid intramuscular injections and invasive procedures 7

Patients on Anticoagulation

• Review all medications including over-the-counter NSAIDs and supplements 3
• Consider dose adjustment or alternative therapy if bruising is excessive

Critical Pitfalls to Avoid

• Never assume normal PT/aPTT rules out all bleeding disorders—these tests miss von Willebrand disease, Factor XIII deficiency, and platelet function disorders 3
• In young children, failure to recognize abuse patterns can result in escalating injury or death 1, 8
• You cannot reliably predict the age of a bruise by its color—16% of bruises were predominantly yellow within the first 24 hours in one study 2
• In chemotherapy patients, waiting for "more serious" bleeding before transfusing increases morbidity and mortality risk 7
• Overlooking medication history, particularly anticoagulants, antiplatelet agents, and steroids 3

When to Refer

Immediate referral to appropriate specialist when 1, 7:

• Suspected child abuse (to child abuse pediatrician and child protective services)
• Confirmed or suspected bleeding disorder (to hematology)
• Chemotherapy patients with thrombocytopenia and active bleeding (to oncology/hematology)
• Suspected connective tissue disorder like Ehlers-Danlos syndrome (to genetics/rheumatology)