What causes easy bruising with normal platelet count?

Easy Bruising with Normal Platelet Count

Easy bruising with a normal platelet count most commonly represents either a platelet function disorder (Type II easy bruising syndrome) or a connective tissue disorder, and requires specific testing beyond routine coagulation studies to identify the underlying cause. 1

Primary Diagnostic Considerations

The differential diagnosis can be systematically approached by recognizing two distinct patterns:

Type I Easy Bruising Syndrome

• Characterized by normal to supranormal platelet function with no identifiable platelet abnormality 2
• Elevated megathrombocyte numbers occur in 60% of cases 2
• Antiplatelet antibodies present in approximately 30% 2
• Predominantly affects women (mean age 35 years) 2
• The bruising tendency likely reflects vascular fragility rather than true hemostatic dysfunction 2

Type II Easy Bruising Syndrome

• Characterized by demonstrable platelet function abnormalities despite normal platelet count 2
• Impaired epinephrine aggregation (primary and secondary wave) in 97% of cases 2
• Impaired connective tissue aggregation in 77% 2
• Impaired ADP aggregation in 42% 2
• Elevated megathrombocyte numbers in 71% 2
• Antiplatelet antibodies present in 38%, suggesting possible autoimmune etiology 2

Essential Diagnostic Testing

Standard PT/aPTT testing is insufficient and will miss the most common causes of easy bruising with normal platelet counts. 1

Initial Laboratory Evaluation

• Complete blood count with platelet count to confirm normal platelet number and evaluate for reactive thrombocytosis 1
• Fibrinogen level to detect fibrinogen defects 1
• PT and aPTT recognizing these do not detect von Willebrand disease, Factor XIII deficiency, or platelet function disorders 1

Specialized Testing Required

• Platelet function studies including platelet aggregation testing with multiple agonists (epinephrine, ADP, collagen, connective tissue) 2
• Von Willebrand factor antigen and activity since VWD is the most common inherited bleeding disorder (prevalence 1 in 1000) and presents with easy bruising 1
• Factor XIII assay if other tests are negative, as this deficiency is not detected by standard screening 1
• Antiplatelet antibody testing given the high prevalence in both types of easy bruising syndrome 2

Associated Conditions to Screen For

Autoimmune Thyroid Disease

• Graves' disease and Hashimoto's thyroiditis are strongly associated with easy bruising and elevated platelet IgG 3
• In patients with thyroid disease and normal platelet counts, 36% (8/22 with Graves', 4/10 with Hashimoto's) have elevated platelet IgG 3
• Twelve of 15 patients with easy bruising had elevated platelet IgG compared to 5 of 22 without bruising (p < 0.001) 3
• Abnormal platelet aggregation (particularly with epinephrine) occurs in 67% of those with elevated platelet IgG 3

Connective Tissue Disorders

• Ehlers-Danlos syndrome (EDS) presents with easy bruising due to capillary and perivascular connective tissue fragility 4
• Easy bruising occurs to variable degrees in all EDS subtypes 4
• Hematological studies including clotting factors, platelet aggregation, and bleeding time are usually normal except for the Hess test (Rumple-Leede test), which indicates capillary fragility 4
• The vascular subtype (Type IV) with collagen III defects carries risk of arterial rupture and severe internal bleeding 4

Medication Review

• NSAIDs, anticoagulants, antiplatelets, steroids, and certain antibiotics increase bruising tendency 1
• Even aspirin withdrawal is relevant, as the original studies excluded patients on antiplatelet agents 2

Critical Pitfalls to Avoid

• Do not assume normal PT/aPTT rules out a bleeding disorder - these tests miss VWD, Factor XIII deficiency, and platelet function disorders 1
• Do not overlook mild hemophilia (Factor VIII or IX deficiency) which can cause significant bleeding even with normal or minimally prolonged aPTT 1
• Do not dismiss the diagnosis based on normal routine coagulation studies - all 75 patients in the landmark study had normal coagulation profiles yet had identifiable abnormalities on specialized testing 2
• Recognize that EDTA-dependent platelet abnormalities exist - if grey platelets are seen on EDTA samples but not citrate, this represents pseudo grey platelet syndrome from EDTA-induced degranulation 5

Age-Specific Considerations

Pediatric Patients

• Transient spontaneous bruising with prolonged bleeding time can occur in healthy children 6
• Associated findings include eosinophilia, positive tourniquet test, and platelet dysfunction (defective ADP release and adhesivity) 6
• This appears to be a self-limited condition of unknown etiology 6

Adult Patients

• Senile purpura results from age-related thinning of blood vessels and skin 1
• Consider liver disease/cirrhosis causing decreased clotting factor production 1
• Screen for malignancies and infiltrative disorders that can cause coagulation abnormalities 1

Management Approach

Treatment depends entirely on identifying the specific underlying cause through the diagnostic algorithm above. The presence of antiplatelet antibodies in 30-38% of cases across both types suggests that some patients may benefit from immunomodulatory approaches, though this requires confirmation of antibody-mediated pathology 2. For connective tissue disorders, management focuses on preventing trauma and vascular complications rather than correcting hemostasis 4.