Supplement I , Vol. 8, Aust. N.Z. J. Med. (19781, pp. 139-132

Polymyositis and Dermatomyositis : Clinical Problems R. L. Dawkins From the Department of Clinical Immunology, Royal Perth Hospital, and Department of Clinical Immunology, Queen Elizabeth I 1 Medical Centre, Perth, Western Australia

Polymyositis comprises a rather heterogeneous group of conditions which are characterised by weakness of skeletal muscle due to inflammatory myopathy. In the presence of certain forms of skin involvement, the term dermatomyositis is usual. Some patients have or develop a coexistent neoplasm. There may be features which are characteristic of connective tissue disorders such as systemic lupus erythematosus, mixed connective tissue disease and systemic sclerosis. Definition In view of the above there has been substantial difficulty in developing satisfactory diagnostic criteria.’.2,3,”For the past three years we have tested the following: ( i ) Symmetrical, proximal and “fixed” weakness and excessive weakness over wasting. “Fixed” is intended to imply stable weakness which shows little variation by the hour or day. (ii Presence of myofibre necrosis as indicated by elevated muscle enzymes and/or muscle biopsy. (iii Inflammation of skeletal muscle indicated by (a) clinical features, such as tenderness; ( b ) non-specific laboratory indices, such as erythrocyte sedimentation rate; and (c) muscle biopsy with particular attention to perivascular mononuclear infiltration. In the light of our assessment the following should be emphasised: ( a ) The three criteria must show some relationship to each other in terms of time. ( b ) Clinical examination for weakness must be thorough with particular attention to aspects such as walking, squatting, sitting from the supine position, raising the head Correspondence: Dr. R . L. Dawkins, Department of Clinical Immunology, Royal Perth Hospital, and Department of Clinical Immunology, Queen Elizabeth I1 Medical Centre, Perth, WA 6000

from the bed and elevation of the upper limbs. It is important to take account of limitation due to pain especially in the presence of synovitis. (c) Muscle biopsy changes are insufficient in themselves but are helpful when taken in conjunction with other features. “Blind” muscle biopsies, i.e. from an area which is not affected clinically, appear to be of rather limited value. The single greatest problem is in the exclusion of closely related conditions. A necrotizing myositis can occur in patients with rheumatoid arthritis and myasthenia gravis without implying that the patient will follow the clinical course of a patient with “pure” polymyositis. There is no evidence to suggest that patients without proximal and “fixed” weakness require high dose corticosteroid therapy. Similar problems exist in patients with established systemic lupus erythematosus and progressive systemic sclerosis. Thus a patient with a defined connective tissue disorder should be treated for that condition rather than polymyositis unless there is convincing evidence of weakness due to necro tizing myo sitis. A major diagnostic problem can arise because patients with definite polymyositis often have some features to suggest an alternative diagnosis, e.g. synovitis, sclerodactyly, Raynaud’s phenomenon, but if these patients satisfy the criteria given above, they should be treated as for polymyositis with modification only if they can be shown to satisfy the full criteria for other disorders such as systemic lupus erythematosus or progressive systemic sclerosis. It would appear very likely that it will be possible to define specific overlap syndromes in the future. It may also become practical to subclassify polymyositis itself. Developments in the delineation of the mixed connective tissue syndrome appear very encouraging (see below). Our assessment has also emphasised the great



importance of considering a systematic differential diagnosis. For example it used to be said that a family history allowed distinction from muscular dystrophy. This is by no means absolute, especially in view of the association between dermatomyositis and C2 deficiency. Furthermore, histologically and in terms of response to Prednisone, there can also be some overlap with dystrophy. Difficulty is also frequent in the case of the thyroid myopathies. It is essential to consider treatable thyroid disease before accepting a diagnosis of polymyositis. Steroid myopathy poses a major problem especially after treatment for polymyositis has been initiated.

ASSOCIATED PHENOMENA Dermatomyositis A significant proportion of patients with polymyositis, as described above, have distinctive skin lesions: ( a ) Heliotrope rash. (b) “Extensor” erythema, with or without scaling over the elbow, metacarpophalangeal and knee joints. (c) Skin oedema and erythema over face, neck, shoulders, upper chest. (d) Periungal erythema and even haemorrhage sometimes associated with desquamation over the fingers. None of these lesions is entirely specific but all are very suggestive and can establish a diagnosis of dermatomyositis as opposed to polymyositis. Their occurrence in the absence of proximal muscle weakness and in the absence of systemic lupus erythematosus identifies the syndrome of “dermatomyositis sine polymyositis”. This syndrome does not appear to warrant high dose corticosteroid therapy, but it must lead to careful consideration of the possibility of an associated neoplasm. Juvenile dermatomyositis appears to be different from the usual adult form. Pathologically there is a systemic angiopathy and clinical features reflect this process as much or more than a necrotising myositis. Associated Neoplasia There is no agreement as to the frequency of neoplasia but it is generally accepted that the





prevalance is increased in patients with polymyositis. A frequency of approximately 200; has been suggested and this accords with our own experience. The type of tumour varies considerably and there is no substantial evidence that the distribution of different cancers is any different from that which occurs in the population as a whole. An exception may be thymoma. It would be very valuable to know which patients should be surveyed exhaustively for the presence of an associated neoplasm. In the absence of better information we have been guided by advanced years, male sex, skin lesions of dermatomyositis, dysphagia, fulminant course and a poor response to corticosteroid therapy. Since adequate treatment of the associated neoplasm has appeared to benefit polymyositis itself it may be important to consider such therapy before embarking on corticosteroids, especially in view of the possibility that immunosuppressive therapy may be contra-indicated in terms of the neoplasm.

Other Connective Tissue Diseuses There is little doubt that polymyositis can occur in association with fully fledged rheumatoid arthritis and perhaps other connective tissue disorders. More commonly, polymyositis/ dermatomyositis is associated with some underlying features of these diseases, e.g. seronegative nonerosive synovitis in the absence of the full picture of rheumatoid arthritis. Similar relationships appear to exist between polymyositis and fibrosing alveolitis. The significance of these apparent overlaps is uncertain, but it is interesting that features such as Raynaud’s phenomenon and synovitis may be indications of a lower frequency of associated neoplasm possibly because these patients have mixed connective tissue disease, rather than polymyositis per se. Myasthenia Gravis and Thymic Disease It is well known that polymyositis can be associated with t h y m ~ m a This . ~ appears to be true in the absence of myasthenia gravis. On the other hand, myasthenia gravis may itself be associated with polymyositis. For these reasons it is important that myasthenia (fluctuating weakness with fatigability) should be carefully




differentiated from myasthenia gravis when it occurs in association with polymyositis. We have previously suggested that myasthenia gravis and myositis represent different immunological reactions, although clearly these can occur together, especially in the presence of a thymoma.2

Diagnosis The general criteria for the diagnosis have been suggested above. The major problem relates to exclusions. In this regard the significance of antiribonuclear protein and related antibodies6 is as yet uncertain. In the local series it appears that some patients previously classified as polymyositis might be more correctly considered mixed connective tissue disease because of the presence of anti-RNP together with compatible clinical features. It may be that MCTD requires lower dose Prednisone therapy. The complications are somewhat different from those associated with polymyositis as a whole. For example we have seen trigeminal neuropathy in association with MCTD, but not polymyositis. Finally, as suggested above, the incidence of neoplasia may be quite different in MCTD. The other important development in the diagnosis of polymyositis appears to be needle biopsies.’ This technique is easy to perform and yields samples which are quite suitable for histological and other assessments. The complications appear to be minimal and multiple


muscles can be sampled. Because of this development it would appear that the incidence of negative biopsies due to sampling errors should decrease. Treatment High dose daily Prednisone (e.g. 60-80 mg per day) appears necessary once one establishes a definite diagnosis of polymyositis. The dosage should be decreased gradually taking account of clinical features and serum enzyme changes. Whilst it is important to be aware of the problem of steroid myopathy (often confused with steroid refractory polymyositis) we have seen more problems related to inadequate treatment and to rapid reduction than to complications of Prednisone. The place of alternate day therapy and cytotoxic treatment remains to be determined.

References 1. BOHAN,A. and PETERS, J . B. (1975): Polymyositis and dermatomyositis, New Engl. J. Mpd. 292, 344, 403. DAWKINS. R. L. (1975): Experimental autoallergic myositis, polymyositis and myasthenia gravis: Autoimmune muscle disease associated with immunodeficiency and neoplasia, Clin. exp. lmmunoi. 21, 185. 3. DAWKINS,R . L: Muscle disease. In: Immunology in Medicine. Editor?, Holborow, E. J. and Reeves, W. G. Academic PressIGrune and Stratton. (In Press.) 4 PEARSON, C. M. and BOHAN,A. (1977): The spectrum of polymyositis and dermatomyositis. In: Medical Clinrcs of North America, Vol. 61, Ed. Shearn, M., W. B. Saunders Company Philadelphia, p. 439. 5 . SOUADXIAN, J. V., ENRIQLIEZ, P. SILVERSTEIN, M. N. and PEPIN,1.-M. (1974): The spectrum of diseases associated with thymoma, Arch. inrern. Med. 134, 374. 6. WOLFE,J. F , ADELSTEIN. E. and SHARP,G. C. (1977): Antinuclear antibody with distinct specificity for polymyositis, J. clm. Invest. 59, 176. 7. EDWARDS,R. H. T., MUNDER,C., JONES, D. A. and BATRA,G. 1. (1975): Needle biopsy for muscle chemistry, Lance1 1, 736.


Discussion Grennan: How helpful do you find electromyography (EMG) as an aid to diagnosis in polymyositis? Does it help you choose your biopsy site? Dawkins: We do not find EMG very helpful at all. EMG seems to have a lower specificity than biopsy and in patients posing a diagnostic problem false positives may result from a number of factors such as disuse atrophy. Furthermore, you cannot biopsy at the site of EMG needle insertion because the needle will produce necrotic lesions.

Burry: Many units find EMG very helpful. The important diagnostic tests for polymyositis are the creatine phosphokinase (CPK) levels, EMG and biopsy. If one can demonstrate abnormalities in two of these three tests in association with a typical clinical picture, a diagnosis of polymyositis becomes almost certain. Since biopsy may be positive in only 60% of cases the EMG becomes a most useful test. Maini: Muscle biopsy is the ultimate arbiter of a



pathological diagnosis in polymyositis. For evidence of muscle necrosis one requires both a positive biopsy and elevation of enzyme levels. However, rheumatologists are sometimes faced with muscle disorders in which the biopsy and enzyme levels are normal but the EMG does show an abnormality. My plea would be that since we d o not have a very clear understanding of some of the disorders in this clinical spectrum we should be using as many techniques as we are able to clarify the situation.

Dawkins: I should have mentioned histochemistry and other techniques which can be used to exclude conditions which can be confused with polymyositis. Klestov: I have recently seen a case of acute fulminating myositis which was very difficult to treat. How would you manage such a patient and how commonly d o you see them? D a wkins: I think it is a frequent enough problem. There is relatively little controversy about treatment; one uses high dose prednisolone (80 mg daily or more) and then one awaits a response. If the patient still has symptoms such as severe dysphagia after a week or so, additional therapy may be necessary. There are differing opinions about subsequent measures, for example, whether one should use steroids in massive doses or add cytotoxic drugs. It is amazing how severe disease can respond quickly. Webb

Dr. Klestov was referring to acute massive rhabdomyolysis which seems to be a fulminant situation and in our experience has a grave prognosis. Dawkins: My impression is that fulminant myolysis is a





different disease but it can occur in the same clinical setting in association with tumours and with some skin features. I agree the prognosis is poor but some patients do survive.

Robinson: This clinical picture does rarely occur in patients with polymyositis who appear to have been well controlled on steroids for some time but suddenly develop catastrophic generalised muscle necrosis.

Room: The use of urinary creatine excretion to distinguish between polymyositis and steroid induced myopathy has been described.' We have found this unhelpful. Could you comment? Dawkins: We have not evaluated this. Douglas: In patients with stable and clinically controlled polymyositis is persistent elevation of the CPK an indication to increase the steroid dose? Should one aim to reduce the CPK to within the normal range? Dawkins: I wish I knew the answer. In the short term one can sometimes see a reduction in the CPK level but not to the extent expected and in this case most clinicians would rely more on the clinical evidence than on the CPK level. The other situation is the long term management in which the patient appears to be doing well but with the CPK increased two to three times the normal level. I am not aware of any evidence suggesting that the level must be reduced to exactly normal.

Reference I. ASKARI,A ,VIGNOS,P J. and MCJSKOWITZ, R. W. (1976):Steroid myopdthy in connective tissuc disease, Amcr. .IMed 61, 485.

Polymyositis and dermatomyositis: clinical problems.

Supplement I , Vol. 8, Aust. N.Z. J. Med. (19781, pp. 139-132 Polymyositis and Dermatomyositis : Clinical Problems R. L. Dawkins From the Department...
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