Acute necrotizing myopathy

Clinical features
An acute necrotizing myopathy has been reported in a few patients with cancer of the lung, bladder, breast, and gastrointestinal tract. The syndrome is characterized by rapid progression, over 1 to 3 months, of symmetrical, predominantly proximal weakness leading to severe functional disability. Serum creatine kinase is markedly elevated and electrophysiological studies demonstrate myopathic findings. Muscle biopsy shows patchy necrosis and perimysial phosphatase staining with little inflammation.

It is unknown if this syndrome represents a severe form of polymyositis. In one patient with necrotizing myopathy and bladder cancer the muscle biopsy demonstrated abnormal, thick "pipestem" capillaries with deposits of complement membrane attack complex (MAC), suggesting an immune-mediated microangopathy different from that observed in patients with dermatomyositis.
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Associated antibodies
No antibodies are associated with necrotizing myopathy, except for one case with myositis, colon cancer and antibody to a muscle protein.

Treatment
Some patients improve with successful treatment of the tumour. Immunosuppression, including corticosteroids, may be tried.

Selected references

1. Levin MI, Mozaffar T, Taher M. et al. Paraneoplastic necrotizing myopathy. Clinical and pathological features. Neurology, 1998: 50; 764-7.
2. Brownell B, Hughes JT. Degeneration of muscle in association with carcinoma of the bronchus. J Neurol Neurosurg Psychiatry 1975;38:363-70.
3. Emslie AM, Engel AG. Necrotizing myopathy with pipestem capillaries, microvascular deposits of the complement membrane attack complex(MAC) and minimal cellular infiltration. Neurology 1991;41:936-9.
4. Bronner IM, Hoogendijk JE, Wintzen AR, et al. Necrotising myopathy, an unusual presentation of a steroid-responsive myopathy. J Neurol 2003;250:480-5.

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