What are the causes of bruising?

Causes of Bruising

Bruising results from bleeding disorders, medications, vascular abnormalities, vitamin deficiencies, liver disease, or trauma—with von Willebrand disease being the most common inherited cause and anticoagulant medications being the most common acquired cause. 1

Bleeding Disorders

• Von Willebrand disease (VWD) is the most common inherited bleeding disorder, affecting approximately 1 in 1000 people, and presents with mucocutaneous bleeding and easy bruising. 1
• Hemophilia (Factor VIII or IX deficiency) causes significant bruising and bleeding even with mild deficiencies, particularly in males. 1
• Immune thrombocytopenia (ITP) is characterized by low platelet count and can cause spontaneous bruising. 1
• Platelet function disorders can cause bruising despite normal platelet counts, requiring specialized testing such as platelet aggregation studies or flow cytometry. 1
• Factor XIII deficiency is not detected by standard PT/aPTT screening but can cause significant bruising. 1

Medication-Related Causes

• Anticoagulants (such as warfarin) are a leading cause of excessive bruising, with bruising being an early manifestation of anticoagulation beyond safe levels. 2
• Antiplatelet agents, NSAIDs, steroids, and certain antibiotics increase bruising tendency. 1
• Patients on warfarin should be counseled to avoid activities that may result in traumatic injury and to report unusual bruising immediately. 2

Vitamin Deficiencies

• Vitamin K deficiency presents with prolonged PT and possibly aPTT, and is particularly important in infants who haven't received vitamin K prophylaxis at birth. 1
• A vitamin K challenge is indicated when PT is abnormal but PTT is normal. 3

Vascular and Connective Tissue Disorders

• Senile purpura results from thinning of blood vessels and skin with aging. 1
• Arteriovenous malformations can cause localized bleeding and bruising. 1

Systemic Medical Conditions

• Liver disease/cirrhosis leads to decreased production of clotting factors and spontaneous bruising, with both PT and PTT typically prolonged. 1, 3
• Disseminated intravascular coagulation (DIC) can cause any type of bruising or bleeding, including life-threatening hemorrhage. 1
• Malignancies and infiltrative disorders cause thrombocytopenia or coagulation abnormalities. 1

Diagnostic Algorithm

Initial Laboratory Testing

• Complete blood count with platelet count to evaluate for thrombocytopenia. 1
• PT and aPTT can detect most factor deficiencies but miss VWD, Factor XIII deficiency, and platelet function disorders. 1
• Fibrinogen concentration and thrombin time to detect fibrinogen defects. 1

Interpretation Based on Results

• If PT and aPTT are both normal, there is high likelihood of von Willebrand disease or platelet function disorder—proceed with VWD-specific testing (VWF antigen, VWF ristocetin cofactor activity, Factor VIII coagulant activity). 1
• If PT is normal but aPTT is prolonged, perform a mixing study to evaluate for intrinsic pathway deficits. 3
• If PT is abnormal but aPTT is normal, consider vitamin K deficiency and perform a vitamin K challenge. 3
• If both PT and aPTT are prolonged, evaluate for liver disease, vitamin K deficiency, or DIC. 1

When to Refer to Hematology

• When specialized testing is needed (platelet function studies, VWD multimer analysis, Factor XIII assay). 1
• When initial screening tests are normal but clinical suspicion for bleeding disorder remains high. 3

Critical Clinical Pitfalls

• Never assume normal PT/aPTT rules out bleeding disorders—these tests miss von Willebrand disease, Factor XIII deficiency, and platelet function disorders. 1
• Patients can have significant bleeding with normal or elevated platelet counts due to qualitative platelet defects or acquired von Willebrand syndrome. 1
• In children, bruising across the back or in non-mobile infants is highly concerning for non-accidental trauma and requires immediate evaluation, though bleeding disorders must also be considered. 4
• Before any surgical procedure, patients with easy bruising require screening with CBC, platelet count, platelet function study, and von Willebrand screen, even if platelet count is normal. 1