What causes unexplained bruising to the arms and how is it diagnosed and treated?

Unexplained Bruising to Arms: Evaluation and Management

Initial Assessment Priority

Begin by determining if the bruising pattern suggests trauma (accidental or non-accidental) versus an underlying bleeding disorder, as this fundamentally changes your diagnostic approach and urgency. 1

The evaluation excludes the need for bleeding disorder workup if: 1

• The trauma history sufficiently explains the bruising pattern
• An independent witness can verify the mechanism of injury
• Object or hand-patterned bruising is clearly present (suggesting abuse)

Critical Historical Features to Obtain

Bruising Characteristics

• Location and pattern: Bruising in non-mobile areas or unusual distributions raises concern 1
• Timing: Preceded by burning/stinging sensation followed by warmth, puffiness, and erythema suggests psychogenic causes 2
• Frequency: Recurrent spontaneous bruising without adequate trauma history 3
• Associated symptoms: Bleeding from other sites (gums, nose, GI tract, genitourinary) 1, 3

Medication and Supplement History

• Any medications or alternative therapies that increase bleeding risk 1
• Recent immune checkpoint inhibitor therapy (can cause thrombocytopenia or hemolytic anemia) 1

Personal and Family Bleeding History

• Previous unexplained bruising episodes 1, 4
• Family history of bleeding disorders (hemophilia, von Willebrand disease) 1, 5
• Easy bruising with minor procedures (dental work, minor cuts) 3, 6

Physical Examination Essentials

Examine for specific bleeding manifestations beyond simple bruising: 1, 5

• Petechiae: Small, flat, non-blanching red/purple spots indicating platelet disorders 5
• Purpura: Larger non-blanching purple/red patches suggesting coagulopathy 5
• Distribution: Dependent areas or pressure points suggest bleeding disorders 1, 5
• Signs of trauma: Torn frenulum, rib tenderness, limb deformities, retinal hemorrhages 1
• Skin integrity: Evidence of self-inflicted injury (purpura factitia) 2

Laboratory Evaluation

Order initial coagulation screening when trauma history is inadequate or absent: 1

First-Line Tests

• Complete blood count with platelet count 5, 6
• Prothrombin time (PT) 1
• Activated partial thromboplastin time (aPTT) 1
• Fibrinogen level 1

Critical Limitations of Screening Tests

PT and aPTT miss several important bleeding disorders: 1

• Von Willebrand disease requires specific testing (not detected by PT/aPTT) 1
• Factor XIII deficiency requires specific assays 1
• Mild hemophilia (factor VIII or IX deficiency) may not prolong aPTT 1

Additional Testing When Initial Screens Are Normal

If bruising persists with normal initial tests, consider: 3, 6

• Von Willebrand factor antigen and activity
• Factor VIII and IX levels
• Platelet function studies
• Factor XIII assay

Differential Diagnosis Framework

Bleeding Disorders

• Platelet disorders: Immune thrombocytopenia, drug-induced thrombocytopenia 1, 5
• Coagulation factor deficiencies: Hemophilia, von Willebrand disease 1, 5
• Acquired inhibitors: Transient coagulation inhibitors (rare but important) 7

Vascular/Connective Tissue Disorders

• Ehlers-Danlos syndrome (collagen biosynthesis failure) 2
• Vitamin C deficiency (scurvy) 2
• Senile purpura 2

Psychogenic Causes

• Recurrent spontaneous bruising with normal coagulation studies in patients with emotional disorders 2
• Distinguished from purpura factitia (self-inflicted) by observation and psychiatric evaluation 2

Non-Accidental Injury

High suspicion when: 1, 4

• Multiple or changing versions of injury history
• History inconsistent with developmental stage
• Bruising in non-mobile infants
• Patterned bruising (hand marks, objects)

Management Approach

When Bleeding Disorder Is Identified

• Hematology referral for specific factor replacement or treatment 3, 6
• Avoid antiplatelet agents and NSAIDs 3
• Educate on injury prevention and when to seek care 6

When Abuse Is Suspected

• Mandatory reporting to child protective services 1, 4
• Consider child abuse pediatrician consultation 1
• Document thoroughly with photographs and detailed descriptions 4

When Evaluation Is Normal

• Reassurance if bruising is minimal and consistent with normal activity 3
• Consider psychogenic causes in recurrent cases with emotional distress 2
• Psychiatric referral for suspected psychogenic purpura 2

Common Pitfalls to Avoid

Do not assume normal PT/aPTT excludes all bleeding disorders - von Willebrand disease and mild hemophilia can present with normal screening tests 1

Do not dismiss bruising in patients with proven bleeding disorders if the pattern suggests abuse - NAI can occur even in children with legitimate coagulopathies 6

Do not overlook medication-induced causes - immune checkpoint inhibitors and other drugs can cause delayed thrombocytopenia 1