Anti-neutrophilic cytoplasmic antibody (ANCA)-associated vasculitis is a primary
systemic vasculitis that affects the small vessels, and ANCA is involved as the
common pathogenesis. Environmental factors such as infectious agents have been
considered to play a role in triggering the autoimmunity. We report here on a case
of ANCA-associated vasculitis that developed after scrub typhus. A 64-year-old
male was admitted because of fever, chills, pain, weakness and hypoesthesia of
his calves. He was diagnosed as having scrub typhus based on the findings of an
eschar and the positive serum anti-orientia antibody. The fever continued despite
the antibiotic treatment. Neurologic symptoms such as numbness, hypoesthesia
and weakness began to develop in the hands, feet and calves with a persisting
fever. The nerve conduction velocity study revealed mononeuritis multiplex of the
superficial peroneal nerve and the median nerve. Microscopic hematuria then
additionally developed, and the serology showed a positive myeloperoxidase
(MPO) test. A nerve biopsy was conducted on the left superficial peroneal
nerve and the result showed non-infectious systemic vasculitis of the mediumsmall
arteries. He was diagnosed as having microscopic polyangiitis along with
ANCA associated vasculitis. The fever resolved and the neurologic symptoms
began to improve after steroid pulse treatment (methylprednisolone 1 g/day). The
neuropathy gradually improved after discharge. We presume that the ANCAassociated
vasculitis was triggered by scrub typhus.