A 50 year old female presents with a six-month history of " painful red spots " on her lower legs. They occur in crops over a period of time and resolve with residual hyperpigmentation. She has no systemic features such as fever or weight loss, and no circulatory, pulmonary, gastrointestinal, or other symptoms. Her past medical history is unremarkable and she is on no medications. There is no family history of bleeding disorders.

Physical examination is unremarkable except for palpable purpura on both lower extremities. Initial laboratory tests include a normal complete blood count, ESR and urinalysis. A biopsy of a skin lesion reveals leukocytoclastic vasculitis (LCV).

What is the differential diagnosis?

LCV resulting in palpable purpura is secondary to another underlying condition in more than 70% of cases.

These include:

1. Infections
   1. Viral: consider hepatitis B and C, HIV, EBV
   2. Acute bacterial: consider meningococcemia, GC, gram negative bacteremia
   3. Chronic infections: consider SBE, fungal infections
2. Drugs (hypersensitivity vasculitis)
3. Para-proteins (cryoglobulins, macroglobulinemia)
4. Systemic vasculitis: consider ANCA-associated vasculitis (Wegener's Granulomatosis (GPA), Microscopic Polyangiitis (MPA), Churg-Strauss), Polyarteritis Nodosa (PAN)
5. Rheumatic diseases: consider Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA), Polymyositis/Dermatomyositis (PM/DM), Sjogren's syndrome (SS)
6. Miscellaneous: consider malignancy, inflammatory bowel disease (IBD)

What testing is indicated in this patient's work up?

The following tests can be done to look for systemic causes of LCV:

• CBC
• ESR
• UA
• ANA
• RF
• ANCA
• Cryoglobulins
• Serum protein electrophoresis (SPEP)
• Hepatitis B and C serology
• C3 and C4 complement levels
• Echocardiography

All tests were negative or normal.

This patient had LCV of unknown cause, with no evidence of systemic vasculitis, underlying connective tissue disease, or other systemic illness. Treatment in this case often consists of low dose prednisone with a gradual taper. Other medications such as colchicine, anti-histamines and dapsone may be helpful in resistant cases.