What causes easy bruising in a young female with a normal platelet count?

Easy Bruising with Normal Platelet Count in a Young Female

In a 22-year-old female with easy bruising and a platelet count of 410,000/μL, the most likely diagnosis is a mild platelet function disorder or von Willebrand disease, both of which require specific testing beyond routine coagulation studies.

Understanding the Clinical Picture

Your patient presents with a paradox: easy bruising despite a normal (actually elevated) platelet count. This immediately excludes quantitative platelet disorders and points toward either:

• Qualitative platelet dysfunction (the platelets don't work properly despite normal numbers)
• Von Willebrand disease (the most common inherited bleeding disorder, affecting approximately 1 in 1000 people) 1
• Mild coagulation factor deficiencies that standard screening may miss
• Vascular or connective tissue abnormalities

The elevated platelet count (410,000/μL) actually makes this more interesting—it's reactive thrombocytosis, which doesn't cause bleeding but suggests we need to look deeper at platelet function 2.

Initial Diagnostic Approach

Essential History Elements

Bleeding pattern assessment 3, 4:

• Mucocutaneous bleeding (nosebleeds, gum bleeding, heavy menstrual periods) strongly suggests platelet dysfunction or von Willebrand disease
• Deep tissue bleeding (hemarthroses, muscle hematomas) suggests coagulation factor deficiency
• Timing: Immediate bleeding suggests platelet/vascular problems; delayed bleeding suggests factor deficiency

Family history is critical 5:

• Von Willebrand disease is hereditary—ask specifically about bleeding problems in blood relatives
• Easy bruising in family members significantly increases likelihood of inherited disorder 5

Medication review 1, 3:

• NSAIDs, aspirin, anticoagulants, steroids, certain antibiotics all increase bruising tendency
• Even over-the-counter supplements can affect platelet function

Physical Examination Findings

Look for 2, 3:

• Pattern of bruising: Random scattered bruises in typical trauma sites vs. unusual locations
• Size and characteristics: Petechiae vs. larger ecchymoses
• Associated findings: Hepatosplenomegaly, lymphadenopathy (suggests systemic disease)
• Skin quality: Thin skin, poor wound healing (connective tissue disorder)

Laboratory Testing Algorithm

First-Line Tests

Order these immediately 1, 3, 4:

1. Complete blood count with differential - Already done; platelet count is 410,000/μL (normal to high)
2. Peripheral blood smear - Look for platelet size/morphology abnormalities 1
3. PT (Prothrombin Time) - Screens extrinsic and common pathways 1, 3
4. aPTT (Activated Partial Thromboplastin Time) - Screens intrinsic and common pathways 1, 3
5. Fibrinogen level - Detects fibrinogen defects 2, 1

Critical Second-Line Tests (If Initial Tests Normal)

Since PT and aPTT do NOT detect von Willebrand disease or mild platelet disorders 2, 1, you must order:

Von Willebrand disease panel 5:

• VWF antigen (VWF:Ag)
• VWF ristocetin cofactor activity (VWF:RCo)
• Factor VIII coagulant activity
• Calculate VWF:RCo/VWF:Ag ratio to detect qualitative defects

Important caveat: Von Willebrand factor levels can be affected by blood type (Type O has lower levels), stress, inflammation, and hormonal status 3. Repeat testing may be necessary.

Specialized Platelet Function Testing

If von Willebrand testing is normal but suspicion remains high 2, 6:

• Platelet aggregation studies - Requires referral to hematology; detects specific platelet function defects 2
• Historical research identified two patterns in "easy bruising syndrome": Type I with normal platelet function but elevated megathrombocytes (60% of cases), and Type II with abnormal platelet aggregation responses (97% had impaired epinephrine aggregation) 6

Note: PFA-100 testing is no longer recommended by many centers as it misses mild platelet abnormalities and has many confounding factors 2.

Common Pitfalls to Avoid

1. Assuming normal PT/aPTT rules out bleeding disorders - These tests miss von Willebrand disease, Factor XIII deficiency, and platelet function disorders 2, 1

2. Overlooking mild hemophilia - Mild Factor VIII or IX deficiency may not prolong aPTT but can still cause significant bleeding 2

3. Not testing for Factor XIII deficiency - This causes severe bleeding but is completely missed by standard coagulation tests 1

4. Dismissing family history - This provides critical diagnostic clues for inherited disorders 5

5. Single abnormal test interpretation - Von Willebrand factor levels fluctuate; repeat testing is often necessary 5

When to Refer to Hematology

Immediate referral indicated if 5, 4:

• Abnormal initial coagulation studies
• Strong clinical suspicion despite normal initial workup
• Before any surgical procedures in a patient with bleeding history
• Positive von Willebrand disease screening requiring confirmation
• Need for specialized platelet aggregation studies

Special Considerations for Young Females

Menstrual history is essential 1, 3:

• Heavy menstrual bleeding is often the presenting symptom of von Willebrand disease in women
• Ask specifically about: pad/tampon changes per hour, clots larger than a quarter, bleeding through protection, anemia requiring treatment

Hormonal influences 5:

• Estrogen increases von Willebrand factor levels
• Testing should ideally be done when not on hormonal contraception
• Pregnancy planning requires special consideration if bleeding disorder confirmed

Most Likely Diagnosis

Given the clinical presentation of easy bruising with normal platelet count in a young female, von Willebrand disease is statistically most likely (prevalence 1:1000), followed by mild platelet function disorders 1, 6. The diagnostic workup must specifically test for these conditions as they are invisible to routine coagulation screening 2, 1.