1 Internal Medicine Department,
2 Autoimmunity Research Unit, Vall d'Hebron General Hospital and
3 Grup d'Investigació Muscular, Hospital Clínic Provincial, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
SIR, The term inclusion body myositis (IBM) was coined in 1971 by Yunis and Samaha [1] to describe a subset of patients with refractory chronic myositis whose muscle biopsies showed, in addition to inflammation, abnormal muscle fibers containing vacuoles and characteristic filamentous inclusions in the cytoplasm and nuclei. A sporadic and a hereditary form have been recognized [2]. The cause of sporadic IBM is not known and it is considered an idiopathic inflammatory myopathy together with polymyositis and dermatomyositis. In the latter two diseases a number of autoantibodies have been detected, some of them being specific of myositis (anti-Jo-1, other antisynthetases and anti-Mi-2) and others associated with myositis, occurring also in other related conditions (anti-PM-Scl, anti-U1RNP). It has recently been suggested that myositis-specific or myositis-associated autoantibodies do not occur in IBM [3]. We describe the case of a patient with IBM and anti-PM-Scl autoantibodies.
A 36-yr-old woman presented with a history of progressive, proximal, symmetrical muscle weakness of the limb girdles and the neck. Physical examination showed asymmetric proximal and distal muscle weakness of arms and legs. An objective determination of strength assessed by MRC scale showed: neck flexors 3, right and left triceps 3, right iliopsoas 4, right quadriceps 3 and left quadriceps 2.5, right and left anterior tibial 3, left gastrocnemius 4, and all other muscles 5. The patient did not complain of arthralgias, Raynaud's phenomenon, skin changes or dysphagia. Laboratory analysis showed elevated serum creatinine phosphokinase (243 IU/l; normal value<195 IU/l). Fibrillation potentials with positive sharp waves and a mixed pattern of short duration/small-amplitude motor unit potentials, with several long duration high-amplitude motor unit potentials in proximal and distal muscles, were found on electromyogram. A muscle biopsy of left gastrocnemius revealed endomysial inflammatory infiltrates and the presence of rimmed vacuoles characteristic of IBM (Fig. 1). Antinuclear antibodies were positive (1/640 in a nucleolar and nucleoplasmic pattern) and anti-PM-Scl antibodies were found by immunoprecipitation from [35S]methionine-labelled HeLa cell extracts (Fig. 2
). Wide-angle microscopy of nailfolds showed unspecific changes of the capillary bed, without loss of capillaries, and a few enlarged nailfold capillary loops. Treatment with corticosteroids was instituted without significant clinical response. Muscle strength deteriorated progressively during the following 5-yr period, with little subjective improvement after treatment with azathioprine and intravenous immunoglobulin. No features of systemic sclerosis were observed during follow up in this time period.
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Inflammatory myopathies are characterized by distinctive autoantibodies that are associated with certain clinical features and immunogenetic patterns. The anti-PM-Scl autoantibody is directed against a multi-subunit nucleolar and nucleolar protein complex. It has been found in patients with myositis, scleroderma and the polymyositisscleroderma overlap syndrome, which combines myositis, Raynaud's phenomenon, arthritis and interstitial lung disease, but not in IBM patients [9, 10]. This patient did not have any features of scleroderma except for the unspecific nailfold capillary bed changes that could be related tothe presence of the autoantibody. To our knowledge the association of IBM and anti-PM-Scl antibodies has not been described previously. This case adds some evidence to the possible autoimmune basis in patients with IBM.
Notes
Correspondence to: A. Selva-O'Callaghan, C/Siracusa No.12 BIS A, Barcelona 08012, Spain. E-mail: aselva{at}hg.vhebron.es
References
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