How is Immune Complex Mediated Small Vessel Vasculitides diagnosed
In most patients presenting with LCV of unknown cause, the following laboratory tests should be considered to identify a potential etiology and assess for end-organ damage: complete blood count, complete metabolic panel, urinalysis, erythrocyte sedimentation rate/C-reactive protein, antinuclear antibody/rheumatoid factor, C3/C4 complement, ANCA, cryoglobulins, hepatitis B and C serologies, human immunodeficiency virus, serum protein electrophoresis, and chest x-ray.
The laboratory evaluation may frequently be unrevealing and nonspecific, but may provide reassurance regarding the extent of organ involvement as well as prognosis.
Notably, malignancy is the cause of LCV in only 1% of patients. Myelodysplastic syndrome and hairy cell leukemia are the most common malignancies.
Patient evaluation requires a complete medical evaluation and appropriate laboratory tests (see Question #6) depending on the clinical situation. Diagnosis is typically made by skin biopsy identifying the presence of cutaneous vasculitis.
The presence of eosinophils on biopsy may suggest a drug-induced LCV. Direct immunofluorescence evaluation of the skin biopsy can help differentiate IgA vasculitis (IgAV; HSP) from other potential SVV. Other than HSP, skin biopsy cannot discern the etiology of cutaneous vasculitis (infections, drugs, cryoglobulinemia, malignancy, etc.).
Therefore, a complete evaluation must be undertaken comprising history, physical examination, and selected laboratory tests.
