Strongyloidiasis presenting during treatment of low-dose glucocorticoid plus rituximab for anti-signal recognition particle antibody–positive polymyositis: A case report

Strongyloidiasis, an intestinal parasitic infection caused by Strongyloides stercoralis, rarely occurs in Japan. When treated with immunosuppressive drugs, two potentially lethal conditions, hyperinfection and dissemination, may develop in asymptomatic carriers of this parasite. We report the development of strongyloidiasis during treatment of polymyositis with glucocorticoids plus rituximab (RTX). A 44-year-old woman had been diagnosed with anti-signal recognition particle antibody–positive polymyositis with interstitial pneumonia 6 years previously, for which she had recently been receiving prednisolone at 5 mg/day and RTX at 375 mg/m2 twice every 3 months. Her condition appeared to be well controlled. She was admitted to our hospital with a 1-month history of chronic diarrhoea and epigastric pain. Standard microscopic examination of a sample of faeces revealed the presence of S. stercoralis; however, serologic testing for parasites was negative. Treatment with ivermectin alleviated her inflammatory diarrhoea and eradicated the faecal parasites. We believe that our patient had an exacerbation of S. stercoralis infection (hyperinfection syndrome) that was exacerbated by low-dose glucocorticoids plus RTX. Strongyloidiasis should be considered in immunocompromised individuals with unexplained diarrhoea, even in non-endemic areas.