Small vessel vasculitis diagnosed with conchotome muscle biopsy: A case series.

A percutaneous conchotome muscle biopsy, which is a semi-open technique, provides significant diagnostic yield, especially for inflammatory myopathies. In patients with small vessel vasculitis, muscle involvement could sometimes be the sole or most prominent organ involvement. While open muscle biopsy has been reported to be useful for the diagnosis of vasculitis, the diagnostic utility with conchotome muscle biopsy for vasculitis remains unclear. Here, we report four cases in which a conchotome muscle biopsy made a significant contribution to their diagnosis of small vessel vasculitis. All cases presented with myalgia and weakness at the onset of their diseases, and with an elevation of myeloperoxidase antineutrophil cytoplasmic antibodies. Pathological examination of muscle tissues revealed significant inflammatory infiltration with fibrinoid necrosis in perimysial arterioles, measuring 50-100 mm in diameter, in all of four cases. Disruption of the elastic plates of the arterioles was found with Elastica van Gieson staining in three cases. Low levels of patients' pain, evaluated with a visual analogue scale (0-100), ranging from 0 to 30, and no occurrence of adverse events in our cases indicated the safety of this technique. All patients were treated successfully with glucocorticoids, with or without immunosuppressants. The conchotome muscle biopsy could yield the pathological features of small vessel vasculitis with minimal invasiveness.