A further patient with parasitic myositis due to Haycocknema perplexum, a rare entity

A new genus of nematode, Haycocknema perplexum, causing polymyositis in humans, was first described in two Australian patients from Tasmania in 1998. Three patients with myositis due to the same nematode were reported from northern Queensland in 2008. We report the sixth case from Australia, a 50-year-old man, also from Tasmania. He had a 2-year history of progressive weakness, weight loss of 10 kg and dysphagia. Muscle biopsy was initially interpreted as polymyositis with eosinophils. Maximum creatine kinase (CK) level was 5700 U/L and full blood examination was normal. He deteriorated after several months of treatment with prednisolone and methotrexate and review of the muscle biopsy showed intramyofibre parasites of H. perplexum. After 3 months of treatment with albendazole therapy, he made a very good clinical recovery and his CK decreased to 470 U/L. This uniquely Australian parasite can mimic polymyositis and leads to significant irreversible morbidity (two of the previous patients still have weakness and elevated CK after years) and even mortality (one died), if diagnosed late or after corticosteroids. Diagnosis can only be made by histopathology of muscle biopsy.