What is the approach to a 17-year-old female with easy bruising on the lower limb and a normal platelet (plt) count of 169?

Approach to Easy Bruising with Normal Platelet Count in a 17-Year-Old Female

This patient with easy bruising and a normal platelet count of 169,000/μL does not require treatment and should be evaluated for non-thrombocytopenic causes of bruising, including inherited platelet function disorders, connective tissue disorders, or benign "easy bruising syndrome."

Initial Assessment

Key Historical Features to Elicit

• Bleeding severity and pattern: Document specific sites of bruising (lower limbs only vs. generalized), size of bruises, and whether they occur spontaneously or with minor trauma 1
• Mucosal bleeding symptoms: Ask specifically about epistaxis, gingival bleeding, menorrhagia (particularly important in adolescent females), and gastrointestinal bleeding 1, 2
• Family history: Heritable bleeding disorders are common; document any relatives with easy bruising, excessive bleeding with surgery/dental procedures, or diagnosed bleeding disorders 1, 3
• Medication history: Aspirin, NSAIDs, antiplatelet agents, and anticoagulants must be excluded 4
• Joint hypermobility and skin findings: Assess for Ehlers-Danlos syndrome features including skin hyperextensibility, joint hypermobility, and atrophic scarring 5

Physical Examination Specifics

• Bruise characteristics: Note size, distribution (dependent areas suggest capillary fragility), color, and whether they are consistent with reported trauma 1
• Petechiae vs. ecchymoses: Petechiae suggest platelet or vascular disorders; large ecchymoses alone may indicate connective tissue abnormalities 5
• Joint and skin examination: Check for joint hypermobility, skin hyperextensibility, and vascular fragility signs (Hess test positivity) to evaluate for connective tissue disorders 5
• Splenomegaly: Palpate for splenomegaly which would suggest alternative diagnoses 3

Laboratory Evaluation

First-Line Testing

• Complete blood count with peripheral smear: Confirm true platelet count (exclude pseudothrombocytopenia), assess platelet size, and evaluate for other cytopenias 1, 6
• Coagulation studies: PT/INR and aPTT to evaluate clotting cascade function 1
• Fibrinogen level: Complete the basic coagulation assessment 1

In this patient with platelet count 169,000/μL and isolated lower limb bruising, these initial tests will likely be normal, pointing toward a platelet function disorder or vascular/connective tissue abnormality 4.

Second-Line Testing (If Initial Tests Normal)

• Platelet function testing: Including platelet aggregation studies with multiple agonists (ADP, epinephrine, collagen, ristocetin) to identify inherited platelet function disorders 3, 4
• Von Willebrand disease screening: VWF antigen, VWF activity (ristocetin cofactor), and Factor VIII levels 3
• Megathrombocyte count: Elevated megathrombocytes may indicate immune-mediated platelet dysfunction even with normal platelet counts 4

Diagnostic Considerations

"Easy Bruising Syndrome" with Normal Platelet Count

This condition predominantly affects young women (mean age 34-35 years) and can be classified into two types 4:

• Type I (more common): Normal platelet function but elevated megathrombocytes in 60% and antiplatelet antibodies in 30% 4
• Type II: Abnormal platelet function with impaired epinephrine aggregation (97%), impaired collagen aggregation (77%), and elevated megathrombocytes (71%) 4

Inherited Platelet Function Disorders

• These disorders present with mucocutaneous bleeding despite normal platelet counts 3
• Require specialized platelet function testing available only at reference centers 3
• May be mild and only manifest as easy bruising in adolescence 3

Connective Tissue Disorders

• Ehlers-Danlos syndrome: Easy bruising occurs in all subtypes due to capillary and perivascular connective tissue fragility 5
• Coagulation studies and platelet function are typically normal except for positive Hess test (capillary fragility test) 5
• Vascular EDS type is life-threatening but rare; classical and hypermobile types are more common with benign bruising 5

Management Approach

For This Specific Patient

Since the platelet count is 169,000/μL (well above any treatment threshold), no platelet-directed therapy is indicated 7. The management strategy should focus on:

1. Observation and reassurance if history and physical examination suggest benign easy bruising syndrome without significant bleeding symptoms 7, 4

2. Proceed to platelet function testing if there is:

   • Personal history of excessive bleeding with procedures/trauma
   • Family history of bleeding disorders
   • Mucosal bleeding symptoms (especially menorrhagia) 3, 1

3. Evaluate for connective tissue disorders if there are:

   • Joint hypermobility
   • Skin hyperextensibility
   • Atrophic scarring
   • Family history of similar features 5

When Treatment Would Be Considered

• Treatment is only indicated if platelet count drops below 30,000/μL 7
• For platelet function disorders, treatment is typically reserved for procedures or active bleeding, using agents like desmopressin (DDAVP) or antifibrinolytics 3
• Avoid unnecessary platelet transfusions, which provide no benefit in non-thrombocytopenic patients and risk alloimmunization 7

Critical Pitfalls to Avoid

• Do not assume ITP: With a platelet count of 169,000/μL, this is not ITP, which requires thrombocytopenia by definition 3
• Do not transfuse platelets: There is no indication for platelet transfusion with this platelet count 7
• Do not overlook non-accidental trauma: Especially important in adolescents; consider this in the differential diagnosis 1
• Do not miss medication history: Many patients do not consider over-the-counter NSAIDs or supplements as "medications" 4
• Do not delay hematology referral if bleeding is significant: If there is mucosal bleeding, family history of bleeding disorders, or abnormal initial coagulation studies, refer to hematology for specialized testing 8, 1

Follow-Up Strategy

• If benign easy bruising syndrome is suspected: Provide reassurance, document baseline findings, and advise return if bleeding worsens 4
• If platelet function disorder suspected: Refer to hematology for specialized testing that requires 3-15 mL blood and is available at reference centers 3
• Monitor platelet counts: Recheck in 1 month if there is any concern for evolving thrombocytopenia 7