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THE NON-DYSTROPHIC MYOPATHIES JOHN PEARCE, M.B., M.R.C.P., Department of Neurology, the General Infirmary, Leeds

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THE NON-DYSTROPHIC MYOPATHIES JOHN PEARCE, M.B., M.R.C.P., Department of Neurology, the General Infirmary, Leeds Postgrad Med J: first published as 10.1136/pgmj.41.476.347 on 1 June 1965. Downloaded from POSTGRAD. MED. J. (1965), 41, 347 THE NON-DYSTROPHIC MYOPATHIES JOHN PEARCE, M.B., M.R.C.P., Department of Neurology, The General Infirmary, Leeds. THE TERM 'myopathy' is applied to any disorder Polymyositis may affect people of any age, of the muscle fibre, the muscle fibre membrane, but the age of onset is from 30 to 60 in 60% the myoneural junction, or the muscle connect- of cases. The chief symptom is weakness of ive tissue. 'Non-dystrophic myopathy' includes proximal muscles of the arms and/or legs all diseases of muscle excluding those genetically in every case. Distal muscles are affected in determined primary degenerative myopathies, one third, and the neck muscles in two thirds collectively known as Muscular Dystrophy. of patients. Fever, muscular pain and tenderness TABLE 1 are seen most often in the more acute forms, CLASSIFICATION OF NON-DYSTROPHIC MYOPATHIES and their absence should not lead to neglecting 1. Inflammatory Polymyositis as a Myopathy Connective tissue disorders polymyositis possible diagnosis. Other inflammatory mvopathies Acute polymyositis is not common, but may 2. Metabolic Familial periodic paralysis progress rapidly and involve the respiratory Myopathy Muscle glycogenoses muscles, sometimes with a fatal termination Myoglobinuric myopathies within a few weeks or months. Myopathies associated with Subacute and electrolyte imbalance chronic forms are more frequent, and present Unclassified myopathies with a progressive weakness and moderate of shoulder 3. Endocrine Thyrotoxicosis wasting and pelvic girdle muscles. Myopathy Cushing's Syndrome There is sometimes no systemic disturbance, Steroid myopathy and pain and tenderness are lacking. All prox- Hypothyroidism imal muscles tend to be affected, and to an by copyright. Hypoadrenalism equal extent. In patients with the disease of 4. Neoplastic Carcinoma long standing, fibrous contractures, and cal- Myopathy Reticuloses cinosis of subcutaneous and muscle tissues 5. The Myasthenic Myasthenia gravis may develop. Syndrome Thyrotoxic myasthenia Myopathic-myasthenic Dysphagia, Raynaud's phenomenon, joint syndrome of carcinoma pains, and skin rashes are common accompani- ments of muscle weakness, and are important Inflammatory Myopathies clues to the presence of polymyositis. The http://pmj.bmj.com/ Polymyositis acuteness of the onset, and the rate of pro- This term encompasses a group of inflam- gression are enormously variable, and spontane- matory disorders of muscle of varied aetiology. ous but usually incomplete remissions are In some patients the condition is confined to seen. muscle tissues but in most occasionally instances there is The skin lesion of dermatomyositis is seen evidence of some systemic disturbance indicat- in 40% of patients (Pearson, 1964). A violace- ing that the myopathy is only part of a more ous is and erythema characteristic, involves on September 26, 2021 by guest. Protected generalised disease of connective tissues. the Accordingly, polymyositis is classified on a particularly eyelids, face and extensor clinical basis, until our understanding of this aspects of the arms. The heliotrope scaling of disorders as a whole is more eruption of the upper eyelids is virtually group complete. A TABLE 2 diagnostic. diffuse erythema and scaling CLASSIFICATION OF INFLAMMATORY MYOPATHIES eruptions are common but non-specific. Tighten- (Modified from Walton and Adams, 1958) ing of the skin over the face, or the distal (i) Polymyositis with purely muscle involvement- phalanges, which appear tapered and shiny, Acute, Subacute, Chronic. and show small (ii) Polymyositis with connective tissue disease or may telangiectatic patches, dermatomyositis, but muscle involvement are characteristic of the skin involvement of dominant. systemic sclerosis, of which polymyositis may (ii) Polymyositis with connective tissue disease or be symptomatic. In patients of middle or old dermatomyositis, but major involvement is of or primary disease and muscle weakness is not age, polymyositis dermatomyositis may be striking. secondary to neoplastic lesions, and this is (iv) Polymyositis complicating malignant disease. discussed in a later section. Postgrad Med J: first published as 10.1136/pgmj.41.476.347 on 1 June 1965. Downloaded from 348 POSTGRADUATE MEDICAL JOURNAL June, 1965 Polymyositis can usually be distinguished degeneration or necrosis of muscle fibres, (2) from muscular dystrophy by the following basophilic areas of regeneration with swollen features: vesicular nuclei, (3) infiltration of inflammatory (i) Polymyositis is more common in females cells. Varying degrees of phagocytosis and than males, and spontaneous remissions occur. interstitial fibrosis are also common. In childhood dystrophy males predominate, Treatment consists of high doses of pred- and progression though slower, is usually re- nisone, commencing with 20 mg. tds, which lentless without a true remission, although should be reduced very slowly only when periods of temporary arrest occur. considerable clinical improvement has occurred. (ii) Muscle involvement is diffuse in poly- It may take up to 2-3 months before ameliora- myositis, but tends to be patchy and selective tion commences. Thereafter the drug should in dystrophy. be continued for 1-2 years before it is totally (iii) Weakness of the neck muscles, dys- withdrawn. If a should the dose and skin rashes are common relapse occur, phagia in poly- has to be increased until the symptoms are myositis, but rare in muscular dystrophy. again controlled. Occasionally ACTH 60-80 (iv) In polymyositis weakness often exceeds Units daily by intramuscular injection will the wasting of muscles, and in the early stages afford a remission unobtainable by prednisone. the reflexes are preserved; in dystrophy the In a series of 52 patients treated by Barwick wasting usually parallels the degree of weakness, and Walton (1963), 34 recovered or improved, pseudohypertrophy is common, and the re- and the remainder were unchanged, worse, or flexes disappear early in the disease (Walton, died. This included Group IV patients with 1961). malignancy, all of whom fared as anti- Investigations are invaluable in establishing cipated. badly the diagnosis. The ESR is sometimes elevated, but this is inconstant; an elevated gamma Polymyalgia Rheumatica globulin fraction of serum proteins associated This is probably an inflammatory disorder with a decreased albumin fraction (Gavrilescu of the intramuscular connective tissue, not by copyright. in- and Small, 1962) is found in over half the cases. volving muscle fibres (Walton, 1964). The Electromyography (EMG) reveals low- patient is over the age of 60, and has severe, amplitude polyphasic action potentials, on unrelenting aching pains around the neck, maximal voluntary contraction indicating a shoulders and upper arms, sometimes also in- myopathy. Fibrillation and 'saw tooth' poten- volving the buttocks and thighs. Movements tials, and a pseudomyotonic pattern are also of shoulder and hip joints are limited, but frequently seen, and are thought to be associated solely by pain, not by muscular weakness or with muscle fibre irritability. Electromyography arthritis. Physical examination is otherwise is however a random sampling method, and negative, but the ESR is invariably overhttp://pmj.bmj.com/ normal patterns may be obtained for this 50 mm/hr, and a mild normochromic anaemia reason, unless many different areas are sampled. is a common accompaniment. (Gordon, 1960; With this reservation, EMG studies show evi- Bagratuni, 1963). High levels of plasma fib- dence of myopathy in 80% of patients. rinogen (>400 mg./100 ml.) and of alpha- Serum aldolase and SGOT are elevated in 2 globulin values are frequently found. Alestig about half the patients, especially those with and Barr (1963) found evidence of arteritis in the most active disease (Barwick and the temporal arteries in seven out of ten cases, Walton, on September 26, 2021 by guest. Protected 1963). Serum creatine kinase is elevated in and 16 of 21 biopsies of the temporal arteries only one third of cases. (Pearce, Pennington showed similar signs of arteritis in a series and Walton, 1964). These changes are helpful reported by Hamrin, Jonsson, and Landberg in distinguishing polymyositis from endocrine (1964). These findings suggest that giant cell and metabolic myopathies in which normal arteritis and polymyalgia rheumatica are two values are usual. Serum creatine kinase estima- clinical variants of the same disease-an tions are of limited value in separating poly- arteritis of the elderly. The response to pred- myositis from dystrophy unless a small eleva- nisone is dramatic in all patients with poly- tion or normal level are found, which would myalgia, and spontaneous remission occurs favour polymyositis. within approximately two years. Muscle biopsy should be performed on a Connective Tissue Diseases and other proximal muscle-e.g., deltoid or matory Myopathies Inflam- in which EMG studies have not beenquadriceps,performed. The consist of Involvement of muscle is a fairly common typical changes (1) Primary pathological finding in many of the so called Postgrad Med J: first published as 10.1136/pgmj.41.476.347 on 1 June 1965. Downloaded from June, 1965 PEARCE: The Non-Dystrophic Myopathies 349 'auto-immune' collagen diseases (Sokoloff, an autosomal dominant with a predilection for Wilens, Bunim and McEwen, 1950). Signs males. The hypokalaemic variety is characterised
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