Steroid myopathy in connective tissue disease

The efficacy and safety of low-dose corticosteroids for rheumatoid arthritis

Low-dose corticosteroids (defined as less than or equal to 10 mg/d of prednisone or equivalent) are used increasingly for the management of rheumatoid arthritis. They are frequently substituted for nonsteroidal antiinflammatory drugs (NSAIDs), particularly in patients with gastrointestinal or other intolerance to NSAIDs, or as "bridge therapy" while patients await the benefits of delayed-acting, disease-modifying agents. Despite their clinical acceptance, published data concerning efficacy are meager. Adverse effects to low-dose corticosteroids are not so frequent nor so severe as those that occur with higher doses. Nevertheless, alterations in glucose metabolism, cutaneous atrophy, cataracts, and glaucoma are common. Osteoporosis, steroid-myopathy, a steroid-withdrawal syndrome, and dysfunction of the hypothalamic-pituitary-adrenal axis appear in some patients. Osteonecrosis, gastrointestinal, cardiovascular, infectious, or neurological complications probably do not occur. Fetal wastage, prematurity, or congenital malformations have not been proven with this dosage.

Drug-induced myopathies

Myopathies are not an unusual complication of drug therapy. The major symptoms in drug-induced myopathies are proximal muscle weakness, increased muscle enzyme levels, electromyographic changes and histological lesions. Some drug-induced myopathies are associated with neuropathy. Drug-induced myopathies can be classified according to the presence or absence of muscular pain and associated neuropathy. Among painless myopathies, we can distinguish myopathies without neuropathy (corticosteroids), myopathies with neuropathy (colchicine, chloroquine and hydroxychloroquine) and myasthenic syndromes (D-penicillamine, antibiotics, beta-blockers). Among painful myopathies, the classification is similar: painful myopathies may or may not be associated with neuropathies. Painful myopathies include polymyositis (D-penicillamine, cimetidine, zidovudine) and other myopathies without polymyositis (clofibrate, statines, cyclosporin). Among the painful neuromyopathies, eosinophilia-myalgia syndrome is a recently described disorder associated with the use of L-tryptophan. Combinations of drugs (for example, a fibrate and a statine or cyclosporin and colchicine) can induce severe myopathies. If such drugs are used together a vigorous surveillance to detect any sign of myopathy is warranted. Instead of classifying drug-induced myopathies according to clinical features, a histological classification can be proposed. Many drugs can induce vacuolar myopathy (colchicine, chloroquine, amiodarone, cyclosporin, drugs causing hypokalaemia and lipid-lowering agents), some others cause a mitochondrial myopathy (zidovudine) or a necrotizing myopathy as seen with vincristine. Overall, several criteria for reporting drug-induced myopathy can be recommended: lack of pre-existent muscular symptoms, a free period between the beginning of the treatment and the appearance of symptoms, lack of another cause accounting for the myopathy, and complete or incomplete resolution after withdrawal of the treatment. Rechallenge of the treatment is not advisable because of the risk of a serious relapse. The exact mechanisms by which drugs cause myopathies are unknown. Some cases may be due to metabolic changes, whereas others may be immune mediated. Nevertheless, the aspect these conditions have in common is the regression of the myopathy with the discontinuation of the drug.

Skeletal muscle wasting and protein-energy malnutrition in children with a newly diagnosed acute leukemia

The changes in skeletal muscle mass of 14 children with newly diagnosed acute leukemia were studied during the first 24 weeks of antileukemia therapy. A muscle index was calculated from the femoral quadriceps muscle thickness, measured by using an ultrasound method, and from the body surface area. Serum albumin concentration was used as a biochemical indicator of protein status. Some children had muscle wasting before diagnosis. The highest degree of muscle wasting developed by 4 to 6 weeks with an average of 27% decrease of the muscle index. Because of simultaneous increase of adipose tissue (average, 33% at 6 weeks and 37% at 12 weeks), the relative body weight or the limb circumferences did not decrease. Muscle mass recovery occurred within the next 6 months. Our data emphasize that changes in the relative body weight or limb circumferences do not reveal nutritional protein depletion and muscle wasting that occurs in children with newly diagnosed acute leukemia.

Pathologic changes and contractile properties of the diaphragm in corticosteroid myopathy in hamsters: comparison to peripheral muscle

Corticosteroids have been shown to produce a myopathy of peripheral skeletal muscle, characterized predominantly by Type II fiber atrophy. To determine if similar histologic and histochemical changes occur in the diaphragm and whether the in vitro contractile properties of this muscle are adversely affected by steroids, we studied two groups of hamsters. The experimental group received triamcinolone while a control group received saline, both given daily for 3 wk as i.m. injections. Soleus (Sol) and extensor digitorum longus (EDL) muscles and costal diaphragm muscle sections were stained for histologic (hematoxylin and eosin, modified Gomori trichrome) and histochemical (myosin ATPase, succinate dehydrogenase [SDH]) analysis. Muscle fiber proportions and cross-sectional areas (CSA) were measured from myosin ATPase sections. In vitro studies of isometric contractions were carried out on small strips of costal diaphragm, measuring maximal isometric twitch (Pt) and tetanus (Po) tensions, time to peak tension (TTP), half relaxation time (1/2 RT), force-frequency relationship, and fatigue characteristics (60 Hz tetani; duty cycle, 0.5). Triamcinolone treatment resulted in no change in muscle fiber proportions. There was no effect on Type I fiber CSA; however, there was Type IIa (Sol, EDL) and Type IIb (diaphragm, EDL) fiber atrophy in triamcinolone-treated animals. Pt and Po (normalized for weight) of diaphragm strips were not different. There was a prolongation in TTP and 1/2 RT, a left shift in the force-frequency curve, and a reduced fatiguability of triamcinolone-treated diaphragm (P less than 0.05). We conclude that a steroid myopathy could be explained by a loss of muscle mass (Type IIb fiber atrophy) rather than an intrinsic impairment in contractile function.(ABSTRACT TRUNCATED AT 250 WORDS)

Corticosteroid-induced myopathy and the respiratory muscles. Report of two cases

Two women with connective tissue disease developed a characteristic steroid-induced myopathy. Reduced maximal transrespiratory pressures indicated reduced respiratory muscle strength. Gradual steroid dosage tapering resulted in prompt clinical improvement and marked increases in respiratory muscle strength, maximal inspiratory pressure increasing by 33 percent in one patient and by 70 percent in the other. This reversible steroid-induced respiratory muscle weakness may be of great significance in reconsidering long-term steroid therapy in patients with underlying lung disease.

Phrenic nerve function in patients with diaphragmatic weakness and systemic lupus erythematosus

Diaphragmatic weakness has been identified as one of the pulmonary manifestations of systemic lupus erythematosus. Whether this weakness results from a neuropathic or myopathic process has not been established. Thirty patients with SLE were screened for the presence of inspiratory muscle (IM) weakness. Detailed studies were performed in nine with IM weakness. All nine were found to have diaphragmatic weakness (mean +/- SD, maximal transdiaphragmatic pressure 50 +/- 12 cmH2O). Phrenic nerve latencies, evaluated using transcutaneous stimulation, were normal in all individuals excluding a demyelinating neuropathy. Compound diaphragm action potential (CDAP) with phrenic nerve stimulation was normal in six of these nine patients. Reduced CDAP in three of nine patients was consistent either with axonal degeneration of the phrenic nerve or diaphragm myopathy. Nerve conduction and electromyographic studies on peripheral nerves and muscles respectively failed to demonstrate an associated generalized neuropathy or myopathy. We conclude that diaphragmatic weakness in patients with SLE is both common and is very unlikely to be caused by a phrenic neuropathy.

Dermatomyositis

Dermatomyositis and polymyositis are related disorders of unknown cause in which immunologic changes may be important. They sometimes overlap with other collagen vascular diseases, and not infrequently are associated with malignancy. The clinical features of the adult and juvenile forms of the disorder and the visceral manifestations of DM-PM are outlined, along with enzymatic, electromyographic, and histologic aids to diagnosis. While the cutaneous lesions often are resistant to treatment, systemic involvement may respond to corticosteroids or to immunosuppressive drugs. Treatment definitely alters the prognosis in cases not associated with malignancy.

Arthritis rehabilitation. A multifaceted process

Rehabilitation of the patient with arthritis is a multifaceted process that should always involve patient, family, and a wide variety of healthcare professionals and community organizations. The optimal goal is to improve the patient's functional performance. Success depends on correct identification of functionally limiting problems.

Electromyography in infants and children

Electromyography (EMG) is of proven value in the diagnosis of acute and chronic neuromuscular diseases in infants and children. When this technique is combined with nerve conduction studies, including repetitive nerve stimulation studies, it is often possible upon completion of the studies to identify the disorder as one of nerve, neuromuscular junction, or muscle. The purpose of this article is to review the principles and techniques of EMG in infants and children and to describe the EMG findings in several neuromuscular disorders.

Effect of treatment of Cushing's syndrome on skeletal muscle structure and function

The time course of recovery in the myopathy of Cushing's syndrome was studied before and after removal of a pituitary adenoma at hypophysectomy in three patients and an adrenal adenoma in another. Serial measurements were performed of quadriceps force, total muscle mass/body weight, individual fibre size on needle biopsies of the lateral muscle mass of the thigh and skeletal muscle cross-sectional area (CSA) and force/unit CSA on computed (CT) scans of thighs and calves. All patients were weak, and recovery was slow but substantial except in one patient who had persistent Cushing's syndrome. An accompanying increase in overall and type II mean fibre area (MFA) occurred after surgery in the patients with a pituitary adenoma, as did an increase in skeletal muscle CSA and force/unit CSA in both patients having CT scans. The only patient with pronounced muscle wasting showed severe type II fibre atrophy with a reduced total muscle mass/body weight, but muscle morphology and total muscle mass were normal in the other patients. Only in this patient was a significant increase in total muscle mass/body weight noted after surgery. These findings suggest that the increase in muscle mass which may follow hypophysectomy in Cushing's syndrome is due to an increase in individual cell size.

Drug-induced neurological disorders

When a patient presents with a neurological or neuromuscular disorder, it is essential to consider drugs as a possible cause. Drugs can affect virtually any part of the neuraxis and the resulting disorders can usually be classified in terms of the anatomical site affected and the clinical presentation. In general, the signs and symptoms of drug-induced neurological disorders are virtually indistinguishable from those seen in naturally occurring disease but are usually reversible if diagnosed early enough. Cortical depression may produce coma, particularly in overdose cases, but a large number of drugs can also initiate seizures in susceptible individuals. The effects of drugs in the pathogenesis of headaches are certainly underestimated, and the eye, hearing and balance mechanisms can be severely damaged by certain drugs before symptoms prompt investigation. The long term effects of antipsychotic drugs on basal ganglia demand that these drugs are used only when absolutely essential and for as short a period as possible. Finally, there is increasing awareness of the role of drugs in the development of neuromuscular disorders such as peripheral neuropathies, myasthenic syndromes and myopathies.

Death in childhood due to facio-scapulo-humeral dystrophy

Two siblings with facio-scapulo-humeral dystrophy (FSH) had muscle biopsy with light microscopy and histochemistry performed. Rapid disease progression resulted in the death of one child at age 5 years. Such an outcome has not been previously reported.

The splayleg disease: a form of congenital glucocorticoid myopathy?

In countries with modern pig industries an increasing percentage of newborn piglets is affected by congenital myofibrillar hypoplasia, also called splayleg or spraddleleg. The main pathomorphological features of this disease are myofibrillar hypoplasia and degeneration. Glucocorticoid myopathy induced in immature muscles of early postnatal rats and rabbits has a pathomorphology very similar to that of splayleg disease. Also in other respects the splayleg disease resembles the glucocorticoid myopathy, as summarized in this contribution. It is suggested that splayleg might represent a congenital form of glucocorticoid myopathy resulting from stress and hormonal imbalance of pregnant sows which affect the fetuses.

Corticosteroid myopathy: a clinical and pathological study

In six patients with Cushing's syndrome and three with steroid myopathy, the clinical, functional, biochemical and structural characteristics of myopathy are described. Proximal muscle weakness occurred in all the patients, preferentially affected the lower limbs and was accompanied by muscle wasting in all but one patient. Force measurements confirmed quadriceps weakness in every patient. Vastus lateralis muscle biopsies showed light microscopic abnormalities in two of three patients with steroid myopathy and one of five patients with Cushing's syndrome. Type II fibre atrophy was the commonest abnormality. Reduced type II mean fibre areas occurred in all the patients with steroid myopathy and were common in Cushing's syndrome patients. Type I mean fibre areas were also reduced in two of the former group and one of the latter group and two further patients in this group had areas at the lower end of the normal range. Abnormalities in electron microscopy, mitochondrial function tests and chemical content of skeletal muscle were frequent and are described and discussed. A plasma creatine kinase activity (CK) at the lower end of the normal range, a myopathic electromyogram (EMG) and a raised 24-h urinary 3-methylhistidine/creatinine ratio on a creatine free diet were other characteristic findings in both groups of patients.

Glucocorticoid-induced atrophy is not due to impaired excitability of rat muscle

We explored the possibility that glucocorticoid-induced muscle weakness and atrophy resulted from impaired muscle membrane excitability. Male Sprague-Dawley rats received intramuscular injections of dexamethasone, cortisone acetate (equivalent anti-inflammatory doses), or saline for up to 28 days. Temporal patterns of change in muscle mass, twitch and tetanic tension, and membrane potential, cable parameters, and excitability were studied in vitro in the extensor digitorum longus (EDL), soleus (SOL), omohyoid (OMO), caudofemoralis (CF), and the sternomastoid muscles (membrane potential only). the membrane properties of EDL fibers were also studied in vivo (pentobarbital anesthesia). The relative severity of atrophy was OMO greater than CF greater than EDL greater than SOL. Reduction in twitch or tetanic tension never preceded atrophy. The twitch and tetanic tension (per g muscle) increased with glucocorticoid treatment. There were no significant changes in the time course of the twitch or tetanus. Dexamethasone produced more severe atrophy and force reduction than did cortisone acetate. Glucocorticoid treatment produced a depolarization of EDL muscle fibers measured in vitro at 23 degrees C, but this did not appear to be physiologically significant because EDL fibers studied in vivo were not depolarized and had normal action potential amplitudes and thresholds. Glucocorticoid treatment did not change the membrane resistance or capacitance. We conclude that glucocorticoid treatment did not produce muscle weakness by impairing sarcolemmal excitability or excitation-contraction coupling, but that the weakness resulted from muscle atrophy.

Effect of glucocorticoid treatment on the excitability of rat skeletal muscle

Dexamethasone treatment in the rat produced depolarization of extensor digitorum longus (EDL) muscle fibers but not soleus (SOL) fibers studied in vitro at 23 degrees C. The depolarization of EDL fibers was most prominent after 1 day of treatment (treated -77.5 +/- 1.1 mV, control -87.2 +/- 0.8 mV; mean +/- S.E.), and was associated with elevation of the action potential threshold and reduction of the action potential overshoot. In vivo, or in vitro in chloride-free solution, the resting potential and action potential threshold and overshoot of EDL fibers from glucocorticoid-treated and control rats were similar. Sodium currents were studied with a patch voltage clamp. Glucocorticoid treatment did not alter the voltage dependence of sodium channel activation or inactivation in fast twitch muscle fibers. Maximal inward currents occurred at about -29 mV and half-maximal inward currents at about -50 mV. Sodium channels were half inactivated at about -71 mV. Glucocorticoid treatment did not alter the sarcolemmal resistance or capacitance. We conclude that glucocorticoid treatment does not produce muscle weakness or atrophy by altering the excitability of muscle fibers.

Steroid myopathy. Insidious cause of muscle weakness

Steroids are so commonly prescribed for so many conditions that physicians tend to become somewhat cavalier in their use. With drug therapy of any type, however, this tendency can lead to trouble. Steroid myopathy, as occurs in Cushing's syndrome. Can develop with steroid therapy and can cause irreversible atrophy if not detected and treated early.

Necrotizing myopathy associated with steroid therapy. Report of two cases

A range of histological lesions was found in necropsy samples of skeletal muscle from 2 patients on steroid therapy. There were perifascicular necroses, regeneration, atrophy, and sclerosis. These findings disagree with published data from human material; however, they are similar to observations made in experimentally induced steroid myopathy in rabbits.

[Myopathy caused by propoxyphene: report of 2 cases with muscle histochemistry]

The cases of a 43 years old-man with gout and a 24 years-old woman with severe back pain who developed dextro-propoxyphene addiction during pain treatment are reported. They had severe edema and fibrosis of skin, subcutaneous tissue and muscle involving the upper and lower limbs. ESR was elevated, CPK and LDH were normal. EMG in proximal muscles showed decreased duration and voltage of potentials, excess of short polyphasics and increased recruitment (BSAP), with positive waves and fibrillations; distal muscles had fasciculations, fibrillations, positive waves, normal voluntary potentials, decreased recruitment. Lymphography indicate delayed progression of contrast media and obstruction in the thighs. Muscle biopsy on fresh-frozen section and histochemistry showed extensive connective tissue proliferation with intense acid and alkaline phosphatase activity in the perimysial and endomysial area, infiltration of lymphocytes near and around small vessels and capillaries. There were perifascicular and type II fiber atrophy. After discharge the patients returned to propoxyphene addiction and the symptoms who subsided during drug withdrawal come back again. New admission, new drug withdrawal and they were discharged free of symptoms and pathologic changes.

Mandibular growth retardation in corticosteroid-treated juvenile mice

Juvenile mice were treated for up to eight weeks with weekly doses of a synthetic analogue of cortisol:triamcinolone hexacetonide. The mandibular condylar cartilage was studied histologically and histochemically at regular intervals. Morphometric measurements were performed along the mandibular posterior vertical dimension (condylar process and ramus). By the second injection significant morphological changes were noted in the condylar cartilage, followed by retardation of bone growth. The most distinctive feature in the cartilage of triamcinolone-treated mice was a marked increase in the dimension of its mineralized zone concomitant with a significant increase in the number of hypertrophic chondrocytes. The role of condylar cartilage in mandibular growth is discussed.

Distinction between the common symptoms of the phosphate-depletion syndrome and glucocorticoid-induced disease

A phosphate depletion syndrome developed in a steroid-dependent asthmatic patient. Initially, the clinical picture was confused with steroid-associated myopathy rather than the phosphate depletion syndrome which has similar symptoms. The classic biochemical findings led to the correct diagnosis. Cessation of phosphate-binding antacids and phosphorus repletion rapidly corrected the biochemical findings and led to the patient's clinical improvement. Platelet phosphate metabolism was evaluated; it was found to correlate with the phosphorus-depleted state and clinical recovery with phosphate repletion. Attention is drawn to the clinical entity of phosphate depletion which may mimic steroid-induced side effects, both of which may occur in patients receiving steroids and antacids.