What is the cause of unexplained bruising on a 31-year-old female's right upper thigh and a small bruise on her left thigh, with ongoing cardiology management?

History of Present Illness

A 31-year-old female presents to clinic with chief complaint of unexplained bruising on her right upper thigh and a smaller bruise on her left thigh. The patient reports no known trauma or mechanism of injury to explain the bruising. She expresses concern regarding the etiology and sought evaluation. The patient notes she is currently under ongoing care by cardiology and her primary care physician, both of whom are out of town, prompting this visit for assessment.

Key Clinical Considerations for Evaluation

Essential History Elements to Obtain

The most critical initial step is determining whether this represents abnormal bleeding through systematic assessment of bleeding symptoms, medication history, and family history 1, 2, 3.

Bleeding History Assessment

• Personal bleeding history: Prior episodes of easy bruising, prolonged bleeding after dental procedures, surgeries (including minor procedures), or circumcision; epistaxis requiring medical intervention; heavy menstrual bleeding; postpartum hemorrhage 4, 1, 2
• Quantify current bruising: Number, size, and exact locations of bruises; whether bruises appear in typical trauma sites (extremities over bony prominences) versus atypical sites (trunk, face, ears, genitals) 4
• Pattern assessment: Whether bruises are patterned (suggesting trauma) or non-patterned; presence of petechiae at pressure points (clothing lines, infant seat patterns in relevant populations) 4
• Timeline: When bruises first appeared, progression over time, any associated symptoms 3

Medication and Supplement Review

• Anticoagulants and antiplatelets: Aspirin, NSAIDs, warfarin, direct oral anticoagulants, clopidogrel 4, 1
• Other medications: Corticosteroids, certain antibiotics, selective serotonin reuptake inhibitors 1
• Herbal supplements and alternative therapies: Many can predispose to bleeding 4

Family History

• Specific bleeding disorders: Von Willebrand disease (most common inherited bleeding disorder, prevalence 1 in 1000), hemophilia, platelet disorders 1, 2
• Ethnicity considerations: Certain populations have higher rates of specific bleeding disorders 4

Cardiology Management Context

• Cardiac indication: Atrial fibrillation, mechanical heart valves, or other conditions requiring anticoagulation 4
• Current cardiac medications: Particularly anticoagulants or antiplatelets that could explain bruising 4, 1

Physical Examination Priorities

The pattern of bleeding on physical examination distinguishes platelet/vascular disorders from coagulation factor deficiencies 2, 3.

• Mucocutaneous bleeding (petechiae, gingival bleeding, epistaxis): Suggests platelet dysfunction or von Willebrand disease 1, 2
• Deep tissue bleeding (hemarthroses, hematomas, intramuscular bleeding): More characteristic of coagulation factor deficiencies 2
• Skin examination: Joint hypermobility, skin hyperextensibility, or atrophic scarring suggesting Ehlers-Danlos syndrome 1, 5
• Hepatosplenomegaly or lymphadenopathy: May indicate malignancy or infiltrative disorders 1

Initial Laboratory Evaluation

If history or physical examination suggests abnormal bleeding, initial screening should include complete blood count with platelet count, PT, aPTT, and fibrinogen level 1, 2, 3.

Critical Testing Limitations

• PT and aPTT do not detect: Von Willebrand disease, Factor XIII deficiency, or mild platelet disorders 4, 1
• Mild hemophilia (Factor VIII or IX deficiency) may not prolong aPTT but can still cause significant bleeding 4, 1
• Platelet count alone is insufficient: Normal platelet count does not exclude platelet function disorders 1, 2

Red Flags Requiring Urgent Evaluation

• Hemodynamic instability or signs of major bleeding 4
• Bleeding at critical sites: Intracranial, intraspinal, intraocular, pericardial, retroperitoneal 4
• Hemoglobin decrease ≥2 g/dL or transfusion requirement 4
• Concurrent anticoagulation with unexplained bruising: May indicate supratherapeutic levels or underlying bleeding disorder 4

Common Diagnostic Pitfalls

The most frequent error is assuming normal PT/aPTT excludes all bleeding disorders 1. Von Willebrand disease, the most common inherited bleeding disorder, requires specific testing (von Willebrand factor antigen, activity, and Factor VIII levels) 1, 2. Additionally, mild Factor VIII or IX deficiency can cause significant bleeding even with normal aPTT 4, 1.

Disposition Planning

Hematology referral is indicated when initial screening suggests a bleeding disorder or when clinical suspicion remains high despite normal laboratory results 2, 3. Given this patient's cardiology management, coordination between specialties is essential if anticoagulation adjustment is needed 4.