Cutaneous small-vessel vasculitis is a non-ANCA-associated vasculitis of small vessels that affects the skin; involvement of other organs must be absent. Cutaneous small-vessel vasculitis is often idiopathic, but all patients should be evaluated for potential underlying causes, including infections (e.g., HIV, HCV), the use of certain drugs (e.g., propylthiouracil, hydralazine, allopurinol), and other vasculitides (e.g., eosinophilic granulomatosis with polyangiitis). Patients usually present with tender, symmetrical palpable purpura on the lower limbs. Skin biopsy is required to confirm the diagnosis; findings include leukocytoclastic vasculitis. Management depends on the severity and chronicity of the lesions, but NSAIDs and bed rest are usually recommended. Glucocorticoids may be indicated in patients with severe, recurrent, or chronic disease.
A necrotizing vasculitis of cutaneous small vessels caused by immune complex deposition; involvement of organs other than the skin must be absent.
- Idiopathic in 45–55% of cases 
- Potential causes include:
- Autoimmune diseases (e.g., SLE, ANCA vasculitis)
- Infections (e.g., HIV, HCV)
- Use of certain drugs (e.g., propylthiouracil, hydralazine, allopurinol, penicillins, cephalosporin, sulfasalazine, phenytoin)
Patients may report flare triggers such as prolonged sitting or standing, alcohol consumption, or URTIs. 
- Painful, symmetric nonblanching palpable purpura on the lower limbs 
- Other lesions: subcutaneous nodules, urticaria, ulcers, vesicles
- Arthralgias may be present.
If drug-induced, lesions usually appear 7–10 days after exposure.
- Consult dermatology and/or rheumatology.
- Request additional diagnostics to:
- Investigate the underlying etiology
- Rule out systemic vasculitis
- A skin biopsy is needed to confirm the diagnosis.
If lesions are confined to a single location, consider a local factor (e.g., trauma, an insect bite) as the underlying etiology. 
- Indication: Obtain for all patients to confirm the diagnosis.
Findings: leukocytoclastic vasculitis 
- Perivascular neutrophilic infiltrate of postcapillary venules
- Fibrinoid deposits
The pathological mechanism that causes cutaneous small-vessel vasculitis can also cause vasculitides in organs other than the skin, which are categorized as distinct diseases. A skin biopsy is essential to establish a definite diagnosis. 
Consult a dermatologist and/or rheumatologist for all patients.
General principles 
- Treat the underlying etiology (e.g., discontinuation of inciting drugs).
- The need for immunosuppressive therapy depends on disease severity and chronicity.
- Consider preventing complications of glucocorticoid therapy, adverse effects of immunosuppressants, and pneumocystis pneumonia prophylaxis.
Mild disease, single episode
- Bed rest with leg elevation, compression stockings, and moisturization of the skin
- NSAIDs for pain management
Severe, recurrent, or chronic disease
- First line: glucocorticoids (e.g., prednisone)
- If refractory to glucocorticoids or glucocorticoid dose cannot be tapered: glucocorticoid-sparing agents (e.g., colchicine, dapsone, azathioprine)
- Refractory disease: Alternative glucocorticoid-sparing agents (e.g., mycophenolate mofetil, methotrexate, rituximab) may be considered.