Cancer-associated Regional Ischemic Myopathy: A Rare Immune Myopathy (P9-8.008)

Abstract

<h3>Objective:</h3> To describe clinical and pathological features of a rare immune myopathy featured by regional ischemia in the setting of cancer. <h3>Background:</h3> Regional ischemic immune myopathy (RIIM) is a rare disorder attributed to myovasculopathy and considered paraneoplastic. It has a high mortality rate. Contrary to dermatomyositis, where microvasculopathy leads to perifascicular pathology and sometimes muscle ischemia, RIIM is characterized by regional necrosis in border zones between perimysial vessels. <h3>Design/Methods:</h3> Review of patient’s clinical and laboratory findings. <h3>Results:</h3> An 81-year-old man manifested subacute proximal limb weakness, dysphagia, and 25-pound weight loss. He had stage IV prostate cancer, diagnosed 3 months prior to weakness-onset. Examination revealed mild facial weakness, flaccid dysarthria, moderate-to-severe neck and limb girdle weakness and atrophy. Videofluoroscopic swallow study showed severe oropharyngeal dysphagia with aspiration. CK was 689 U/L (normal 39–108 U/L) at presentation but 6,145 U/L six weeks earlier. Myositis-associated and HMGCR antibodies were negative. EMG showed proximal-predominant myopathic changes with fibrillation potentials. Muscle biopsy revealed several well-demarcated areas of ischemia involving adjacent fascicles. Necrotic fibers were in a similar early stage of necrosis with no macrophagic infiltration and diffuse sarcoplasmic C5b-9 deposition. A few small collections of perimysial perivascular inflammatory cells were present in the areas of the specimen not affected by ischemia. There was patchy capillary depletion and dilation; some capillaries in areas not affected by ischemia showed complement deposition. Myxovirus resistance protein A (MxA) expression occurred diffusely, especially in necrotic fibers, but without perifascicular predominance. Patient received IVIG 2g/Kg and prednisone 40 mg daily. The limb weakness stabilized while the dysphagia progressed. He expired 3 weeks later. <h3>Conclusions:</h3> RIIM is a rare myovasculopathy leading to muscle weakness in the setting of cancer. In keeping with published data, it has a poor prognosis. The identification of RIIM myopathological changes should trigger the search for underlying malignancy in patients without known cancer. <b>Disclosure:</b> Dr. Granger has nothing to disclose. Dr. Soontrapa has nothing to disclose. Dr. Klein has a non-compensated relationship as a Klein with Neurology Journal that is relevant to AAN interests or activities. Dr. Milone has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Argenx. Dr. Milone has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Neurology Genetics, AAN. The institution of Dr. Milone has received research support from Mayo Clinic, CCaTS-CBD. The institution of Dr. Milone has received research support from Mayo Clinic, SGP Award. The institution of Dr. Milone has received research support from MDA for Care Center grant. The institution of Dr. Milone has received research support from Regenerative medicine Minnesota.