Cutaneous small vessel vasculitis (ORPHA:889)
A small vessel vasculitis characterized by neutrophilic inflammation predominantly limited to the superficial cutaneous postcapillary venules and without systemic vasculitis or glomerulonephritis. Typical presentation is of unifocal or multifocal palpable purpura on the lower extremities.
Epidemiology
The annual incidence of leukocytoclastic vasculitis in the United States is estimated at 1/220,000, of which 45% consist of cutaneous small vessel vasculitis.
Clinical description
The disease onset can occur at any age, and typically presents with non-blanching, palpable purpura and/or petechiae of the lower extremities with unifocal or multifocal distribution. The lesions may coalesce, ulcerate or be surrounded by hemorrhagic bullae. Urticarial lesion can also be observed. Lesions are usually not painful, although they may cause burning and itching. Histological characteristics are non-specific for the disease and include neutrophilic infiltration of the dermal small blood vessel walls, as well as, fibrinoid necrosis and disruption of the vessel wall, leukocytoclasia, endothelial swelling, and erythrocytes extravasation. As the lesion gets older, neutrophils diminish, and lymphocytes become prominent.
Etiology
The disease may be idiopathic (in up to 50% of cases) or secondary to infections, medications, connective tissue diseases, or malignancy. The disease occurs due to the deposition of immune complexes (IC) on the wall of post-capillary venules, which then activates both complement pathways, leading to degranulation of mast cells and neutrophil chemotaxis.
Diagnostic methods
Diagnosis is one of exclusion. In general, skin biopsy samples from lesions between 24-48 hours old, should be examined with light microscopy and direct immunofluorescence. A complete history, review of systems, physical examination, and selected laboratory studies also should be performed to assess for inciting causes or extracutaneous involvement.
Differential diagnosis
The main differential diagnosis is of systemic small vessel vasculitides with cutaneous presentation and includes antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, cryoglobulinemic vasculitis, immunoglobulin A vasculitis. Other conditions with similar histopathology include infective endocarditis, macular purpura owing to trauma, skin fragility, pigmented purpuric dermatosis, septic emboli, and livedoid vasculopathy.
Management and treatment
Treatment varies and depends on the chronicity of the disease, the severity of cutaneous involvement, and the presence or absence of both an underlying cause. An isolated episode associated with a known inciting factor may be managed by removal or treatment of the trigger, along with symptomatic measures. First-line systemic treatments for chronic, idiopathic disease include colchicine or dapsone, used singly or in combination. Recurrent, chronic, or severely symptomatic disease that does not respond to the aforementioned therapies may require initiation of an immunosuppressive agent such as azathioprine, mycophenolate mofetil, methotrexate, or rituximab.
Prognosis
The clinical outcome is typically good with 90% resolving in weeks to months of onset, but may be complicated by the occurrence of ulcers (treatment prolongation, infections and scarring). The reported relapse rate is between 8-25%.

                            Last update: 
                            October 2020


                            - Expert reviewer(s): 
                            Dr Xavier PUECHAL  - Pr Benjamin TERRIER