What lab work and diagnostic tests are needed for a patient with spontaneous bruising, joint pain, and leg swelling?

Diagnostic Workup for a 39-year-old Male with Spontaneous Bruising, Joint Pain, and Leg Swelling

For a patient presenting with spontaneous bruising, joint pain, and leg swelling, a comprehensive laboratory workup and imaging studies should be performed to evaluate for hematologic disorders, inflammatory conditions, and thromboembolic disease.

Initial Laboratory Tests

• Complete blood count (CBC) with platelet count and peripheral blood smear to assess for thrombocytopenia, leukemia, or other hematologic abnormalities 1
• Coagulation studies including prothrombin time (PT) and partial thromboplastin time (PTT) to evaluate for coagulopathies 1
• Inflammatory markers: erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to assess for inflammatory conditions 2
• Autoimmune panel including antinuclear antibody (ANA), rheumatoid factor (RF), and anti-cyclic citrullinated peptide (anti-CCP) to evaluate for autoimmune arthritis 2
• If symptoms are suggestive of reactive arthritis or affect the spine, consider HLA-B27 testing 2

Imaging Studies

• Plain radiographs of affected joints to evaluate for joint damage, erosions, and to exclude alternative diagnoses such as fractures or tumors 2
• Ultrasound of affected joints and soft tissues to assess for:
  • Joint effusions requiring aspiration 2
  • Synovitis and soft tissue inflammation 2
  • Hematomas or hemarthroses 3
• Doppler ultrasound of the lower extremities if deep vein thrombosis (DVT) is suspected, especially with unilateral leg swelling 2
• Consider MRI of affected joints if ultrasound is inconclusive or if detailed evaluation of soft tissues and bone marrow is needed 2

Specialized Testing

• Joint aspiration (arthrocentesis) for:
  • Cell count and differential 2
  • Crystal analysis to rule out gout or pseudogout 2
  • Gram stain and culture to evaluate for septic arthritis 2
  • Assessment for bloody effusion suggesting hemarthrosis 3
• If DVT is suspected and ultrasound is negative or inconclusive, consider CT venography or MR venography 2
• If platelet count is normal but bleeding tendency persists, consider specialized platelet function testing and von Willebrand disease testing 1

Disease-Specific Testing

• For suspected immune thrombocytopenic purpura (ITP):

  • Platelet antibody testing 4
  • Bone marrow examination if clinically indicated 1

• For suspected rheumatologic disease:

  • Complete autoimmune panel including anti-double stranded DNA, complement levels, and specific antibodies based on clinical suspicion 5
  • Consider testing for antiphospholipid antibodies if there is a history of thrombosis 5

• For suspected nutritional deficiencies:

  • Vitamin C level if dietary history suggests possible scurvy 6
  • Vitamin K level if coagulopathy is present 1

Monitoring and Follow-up Testing

• For patients with inflammatory arthritis, monitor with serial rheumatologic examinations and inflammatory markers every 4-6 weeks after treatment initiation 2
• Repeat imaging may be necessary to evaluate treatment response or disease progression 2

Important Considerations

• If initial testing is inconclusive but clinical suspicion remains high for a bleeding disorder, referral to a hematologist is warranted 1
• In cases of suspected septic arthritis, prompt arthrocentesis is essential for diagnosis and should not be delayed 2
• When evaluating for DVT, a negative highly sensitive D-dimer in a low-risk patient can rule out DVT without further testing 2
• Consider the possibility of medication-induced bleeding or bruising, particularly anticoagulants, antiplatelet agents, or certain supplements 1

Remember that the pattern of joint involvement, chronology of symptoms, and presence of extra-articular manifestations can provide important diagnostic clues in narrowing the differential diagnosis 5.