Blastocystis hominis (B. hominis) is a parasite that often causes gastrointestinal symptoms in patients with immune deficiency and has a controversial pathogenicity in healthy people, although some symptoms are reported outside of the gastrointestinal system in healthy persons. Henoch-Schönlein Purpura (HSP) vasculitis is an acute autoimmune disease characterised by IgA storage of small vessels that is believed to include infectious factors in its aetiology. A 30-month follow-up with a boy diagnosed with HSP being treated with steroid therapy showed that he had recurrent symptoms within two days, and B. hominis was detected in the faecal analysis. His symptoms including rash, abdominal pain, and arthritis improved after treatment with steroid and co-trimaksazol. This paper is the first to present a case of HSP associated with B. hominis.