Summary

Whereas systemic vasculitis is the most common form of vasculitis, vasculitis restricted to a single organ system is rare. Primary vasculitis restricted to striated skeletal muscle has been described in few case reports for polyarteritis nodosa and leucocytoclastic vasculitis, but not for small vessel vasculitis, type microscopic polyangiitis. The authors describe three patients with primary small vessel vasculitis of the skeletal muscle without evidence of other major organ involvement. All three patients presented with myalgias and highly elevated acute phase reactants while muscle weakness and elevated creatine kinase levels were not consistently present. Diagnoses were established by muscle biopsy and extensive search for potential causes of secondary vasculitis. Complete remission could be accomplished by steroids alone in only one case, while additional immunosuppressants were needed in the other two cases. Primary small vessel vasculitis of the skeletal muscle should be considered in patients presenting with myalgia and signs of systemic inflammation in the absence of other organ manifestations. Once diagnosed, aggressive systemic immunosuppression is appropriate.