BACKGROUND: Acute muscular sarcocystosis (AMS) is one of a spectrum of diseases caused by the Sarcocystis parasite which infects humans in regions where it is endemic. Infections present with non-specific signs and symptoms and have been known to occur in clusters.

CASE REPORT: A 51-year-old Vietnamese male presented to Tan Tock Seng Hospital, Singapore with 3 weeks of fever, urticarial rash, non-productive cough, and lower back pain. He had an extensive travel history prior to presentation. Magnetic resonance imaging (MRI) showed myositis involving the paravertebral and upper thigh muscles. The infection was confirmed on open muscle biopsy and Sarcocystis nesbitti was identified on molecular testing. The patient was treated with prednisone and methotrexate.

CONCLUSIONS: AMS must be considered in a patient with history of exposure to an endemic area. Diagnosis of the condition and identification of S. nesbitti as the causative organism will help to further study of this particular condition and guide treatment.

Keywords: Eosinophilia, Magnetic Resonance Imaging, myositis, Sarcocystosis, Polymerase Chain Reaction, creatine kinase, DNA, Protozoan, Myalgia, Sarcocystis, Travel-Related Illness, urticaria