Answer to Dermacase continued from page 748
1. Drug-induced leukocytoclastic vasculitis
Leukocytoclastic vasculitis (LCV) is an uncommon auto-immune disease characterized pathologically by fibrinoid necrosis of the blood vessel wall and immune complex deposition.1 It is characterized by asymptomatic, non-blanching, palpable purpura, most commonly on the legs; however, it can be itchy or burning. Other features of LCV depend on the size of the involved blood vessels. Leukocytoclastic vasculitis is classified according to blood vessel size into 3 main categories (Table 1).2,3 Small-vessel vasculitis, also known as hypersensitivity angiitis and necrotizing venulitis, is characterized by nonblanching, palpable purpura, as seen in our patient. Medium-vessel vasculitis is characterized by subcutaneous nodules, ulcers, livedo reticularis, and digital gangrene. Large-vessel vasculitis rarely presents on the skin.2–5
Diagnosis
Small-vessel LCV is diagnosed clinically and confirmed by skin biopsy. Skin biopsy should be sent for routine microscopy and direct immunofluorescence. The next step after confirming the diagnosis is to look for the possible cause. Multiple causes have been implicated in the pathogenesis of small-vessel LCV. These include infections, drugs, autoimmune diseases, and malignancies.1–5 Infections that have been implicated in the pathogenesis include streptococcal infections (the most common) and hepatitis B and C. Multiple drugs have been implicated, most commonly nonsteroidal anti-inflammatory drugs, penicillin, furosemide, hydrochlorothiazide, and minocycline. Different autoimmune diseases have been implicated, including systemic lupus erythematosus and rheumatoid arthritis. Small-vessel LCV can present as a paraneoplastic condition, most commonly associated with hematologic malignancies. However, LCV is most commonly idiopathic.5
Regardless of the cause of LCV, noncutaneous involvement should be ruled out. Blood tests for the following should be done: complete blood count, erythrocyte sedimentation rate, C-reactive protein level, and kidney and liver function. Urinalysis and urine microscopy should also be done. Other investigations depend mainly on the patient’s medical history and physical examination findings (eg, antinuclear antibody level, C3 and C4 levels, immunoglobulin A level, serum protein electrophoresis, and throat culture) (Box 1).
Differential diagnosis
Small-vessel LCV on the legs can be mistaken for petechiae, stasis dermatitis, and pigmented purpuric dermatosis. Petechiae are pinpoint-sized, nonpalpable red macules. Stasis dermatitis is a pruritic condition seen in people with evidence of venous insufficiency (eg, with dilated veins and hemosiderin deposition on the skin). Pigmented purpuric dermatosis is characterized by partially palpable, usually asymptomatic, macules that develop gradually over months.
Recommended investigations
|
c-ANCA—cytoplasmic antineutrophil cytoplasmic antibody, ENA—extractable nuclear antigen, p-ANCA—perinuclear antineutrophil cytoplasmic antibody.
Treatment
Mild, skin-limited disease does not require treatment apart from rest and elevation of the legs. However, if a cause is identified, then it should be treated. Presence of arthralgia or arthritis requires use of nonsteroidal anti-inflammatory drugs or a short course of prednisone.5 Most patients will respond to such treatment. However, some patients will become steroid dependent; therefore, steroid-sparing agents should be used. These include dapsone, colchicine, azathioprine, and mycophenolate mofetil. The patient in this case was advised to stop taking hydrochlorothiazide and increase the dose of amlodipine. The rash resolved in 3 weeks.
Footnotes
-
Competing interests
None declared
- Copyright© the College of Family Physicians of Canada