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

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Abstract

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.

Introduction

A new genus of nematode, Haycocknema perplexum, causing polymyositis in humans was first described in two Australian patients from Tasmania in 1998.1, 2 Ten years later, another three patients with myositis due to the same nematode were reported from northern Queensland.3 We report the sixth case from Australia, a 50-year-old man, also from Tasmania.

Section snippets

Clinical features

A 50-year-old Caucasian shipwright presented in December 2010 with a several year history of weakness and weight loss. He had no significant past medical history. In 2008, he first noticed difficulty running up stairs. This weakness progressed over the next 2 years. He also noticed intermittent problems with swallowing, and lost approximately 10 kg. On presentation to his general practitioner in December 2010, there were no objective clinical findings. The only abnormal investigation was an

Pathology of muscle biopsy

There was moderate myositis with endomysial aggregates of lymphocytes, histiocytes and eosinophils associated with actively degenerating and regenerating fibres (Fig. 1). However, there were parasites within myofibres. These included transverse sections of mature female worms containing small numbers of larvae in the uterus; in others, females were not yet gravid. There were also sections through the oesophagus of the parasite containing refractile granules in the rectal region of the female (

Discussion

This is the sixth reported case of a patient with myositis associated with H. perplexum infection and it is interesting that he lived and worked in the same state as the original two patients described in 1998.1 He shared exposure to Tasmanian wildlife, both alive and dead, which may have predisposed him to infection by this unusual nematode.

The clinical and laboratory features of the six reported patientsare listed in Table 1. All patients noted development of weakness over several years,

Acknowledgements

We thank Drs. Craig Costello, Phillip Marshall, John Archer and Jon Reimers for their follow-up of the previously reported cases from northern Queensland.

References (4)

  • X. Dennett et al.

    Polymyositis caused by a new nematode

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    (1998)
  • D.M. Spratt et al.

    Haycocknema perplexum n.g., n. sp. (Nematoda: Robertdollfusidae): an intramyofibre parasite in man

    Syst Parasitol

    (1999)
There are more references available in the full text version of this article.

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