Inflammatory myopathies: Part 1

Adolescent COVID-19-Associated Fatal Rhabdomyolysis

Coronavirus disease 2019 (COVID-19) has become an urgent global health priority. Although most patients with COVID-19 manifest with fever and respiratory tract symptoms, COVID-19 infections may also involve other organs and extrarespiratory manifestations, including cardiac, gastrointestinal, hepatic, renal, and neurological symptoms. This case describes a 16-year-old boy who presented with fever, sore throat, myalgia, and subsequently with shortness of breath. A diagnosis of COVID-19 was confirmed by polymerase chain reaction. His condition deteriorated and he died within 3 days of admission. An evaluation of his past medical history confirmed an episode of viral illness which had progressed to myositis and rhabdomyolysis 1 year prior. Clinicians should be aware of this complication and maintain a high index of suspicion in cases of COVID-19 presenting with extrapulmonary symptoms.

What rheumatologists should know about orofacial manifestations of autoimmune rheumatic diseases

Orofacial manifestations occur frequently in rheumatic diseases and usually represent early signs of disease or of its activity that are still neglected in clinical practice. Among the autoimmune rheumatic diseases with potential for oral manifestations, rheumatoid arthritis (RA), inflammatory myopathies (IM), systemic sclerosis (SSc), systemic lupus erythematosus (SLE), relapsing polychondritis (RP) and Sjögren's syndrome (SS) can be cited. Signs and symptoms such as oral hyposalivation, xerostomia, temporomandibular joint disorders, lesions of the oral mucosa, periodontal disease, dysphagia, and dysphonia may be the first expression of these rheumatic diseases. This article reviews the main orofacial manifestations of rheumatic diseases that may be of interest to the rheumatologist for diagnosis and monitoring of autoimmune rheumatic diseases.

What rheumatologists should know about orofacial manifestations of autoimmune rheumatic diseases

Orofacial manifestations occur frequently in rheumatic diseases and usually represent early signs of disease or of its activity that are still neglected in clinical practice. Among the autoimmune rheumatic diseases with potential for oral manifestations, rheumatoid arthritis (RA), inflammatory myopathies (IM), systemic sclerosis (SSc), systemic lupus erythematosus (SLE), relapsing polychondritis (RP) and Sjögren's syndrome (SS) can be cited. Signs and symptoms such as oral hyposalivation, xerostomia, temporomandibular joint disorders, lesions of the oral mucosa, periodontal disease, dysphagia, and dysphonia may be the first expression of these rheumatic diseases. This article reviews the main orofacial manifestations of rheumatic diseases that may be of interest to the rheumatologist for diagnosis and monitoring of autoimmune rheumatic diseases.

Clinical characteristics and outcomes of juvenile and adult dermatomyositis

Dermatomyositis (DM) is an idiopathic inflammatory myopathy with bimodal onset age distribution. The age of onset is between 5-18 yr in juvenile DM and 45-64 yr in adult DM. DM has a distinct clinical manifestation characterized by proximal muscle weakness, skin rash, extramuscular manifestations (joint contracture, dysphagia, cardiac disturbances, pulmonary symptoms, subcutaneous calcifications), and associated disorders (connective tissue disease, systemic autoimmune diseases, malignancy). The pathogenesis of juvenile and adult DM is presumably similar but there are important differences in some of the clinical manifestations, associated disorders, and outcomes. In this study, we investigated the clinical characteristics and outcomes of 16 patients with juvenile DM and 48 with adult DM. This study recognizes distinctive characteristics of juvenile DM such as higher frequency of neck muscle involvement, subcutaneous calcifications, and better outcomes.

Recurrent myositis triggered by infections: a case report

Introduction

Recurrent myositis triggered by infections is unusual, with only one other case reporting two attacks described in the literature.

Case presentation

We report the case of a 24-year-old Caucasian woman with recurrent myositis triggered by sore throat, respiratory and urinary tract infections, over the past 18 years, up to four times a year. Myositis of this frequency and duration, apparently triggered by infections, has not been reported previously.

Conclusion

We believe that this case adds to the understanding of myositis associated with infections being a triggered autoimmune response, and postulate that the pathogenesis in our patient is a non-specific immune response to a range of different precipitants, both bacterial and viral.

Inflammatory myopathies: clinical, diagnostic and therapeutic aspects

The three major forms of immune-mediated inflammatory myopathy are dermatomyositis (DM), polymyositis (PM), and inclusion-body myositis (IBM). They each have distinctive clinical and histopathologic features that allow the clinician to reach a specific diagnosis in most cases. Magnetic resonance imaging is sometimes helpful, particularly if the diagnosis of IBM is suspected but has not been formally evaluated. Myositis-specific antibodies are not helpful diagnostically but may be of prognostic value; most antibodies have low sensitivity. Muscle biopsy is mandatory to confirm the diagnosis of an inflammatory myopathy and to allow unusual varieties such as eosinophilic, granulomatous, and parasitic myositis, and macrophagic myofasciitis, to be recognized. The treatment of the inflammatory myopathies remains largely empirical and relies upon the use of corticosteroids, immunosuppressive agents, and intravenous immunoglobulin, all of which have nonselective effects on the immune system. Further controlled clinical trials are required to evaluate the relative efficacy of the available therapeutic modalities particularly in combinations, and of newer immunosuppressive agents (mycophenolate mofetil and tacrolimus) and cytokine-based therapies for the treatment of resistant cases of DM, PM, and IBM. Improved understanding of the molecular mechanisms of muscle injury in the inflammatory myopathies should lead to the development of more specific forms of immunotherapy for these conditions.

Juvenile dermatomyositis: clinical, laboratorial, histological, therapeutical and evolutive parameters of 35 patients

This study was based on a prospective and a retrospective analysis of 35 patients who met Bohan and Peter criteria for juvenile dermatomyositis diagnosis. The mean follow-up time was three years ten months. Calcinosis was present in five (14.28 %) patients, cutaneous ulcers in four (11.42%), and systemic involvement in nine (27.71%) patients. All patients presented alterations in the serum levels of muscle enzymes, and all of them were submitted to muscle biopsy as a diagnostic procedure. Nine (25.71%) patients received corticotherapy prior to and 26 (74.28%) after the muscle biopsy. Chloroquine, methotrexate, cyclosporine, cyclophosphamide and intravenous immunoglobulin were used in patients with poor response to corticotherapy. Continuation of cutaneous manifestations was observed in 4 (11.43%) patients, laboratorial activity in 1 (2.85%), cutaneous and laboratorial activities in 3 (8.57%). Ten (28.57%) patients were out of activity, and 17 (48.57%) in remission at study end-point, on March 2002. Two (5.71%) patients died.

Congenital inflammatory myopathy: a demonstrative case and proposed diagnostic classification

There have been few reports of congenital inflammatory myopathy in the literature, and most of these have been associated with congenital muscular dystrophy. We review the literature and present a case with electromyographic and muscle biopsy evidence of congenital inflammatory myopathy with onset in the perinatal period and no evidence of a congenital muscular dystrophy. There was evidence of subjective improvement following corticosteroid administration (approximately 1 mg/kg per day) with a concomitant normalization of the serum creatine kinase activity. Of particular interest in the case was the history of maternal infection, suggesting a possible postinfectious molecular mimicry as the etiology of the muscle inflammation. This case suggests that a rare form of congenital inflammatory myopathy does exist that is not associated with a congenital muscular dystrophy. A preliminary classification scheme is proposed to separate true congenital cases from those acquired after birth and those cases associated with congenital dystrophy.

Diagnosis of dermatomyositis and polymyositis: a study of 102 cases

Patients with dermatomyositis (DM) or polymyositis (PM) were studied retrospectively. The patients were divided into four groups: definite PM 24, probable PM 19, definite DM 34 and mild-early DM 25 cases. PM patients complained more often proximal muscle weakness [p <0.01]. DM patients complained more arthralgia [p <0.05], dysphagia [p <0.03] and weight loss [p <0.04]. Five patients had a malignant neoplasm and 9 had other connective-tissue disease. DM presented higher ESR than PM [p <0.002]. PM presented more significant increase in creatine kinase (CK) [p <0.02] and in alanine aminotransferase (ALT) [p <0.001] levels. Electromyography showed myopathic pattern in 76%. Muscle biopsy was the definitive test. Perifascicular atrophy was more frequent in definite DM than in mild-early DM group [p <0.03].

CONCLUSION

A small association with connective-tissue diseases and neoplasms was found. DM and PM are clinically different. DM presents systemic involvement affecting the skin, developing more severe arthralgia, dysphagia and weight loss and presenting higher values of ESR. PM presents a restricted and more significant involvement of muscles generating more weakness complaints and higher levels of serum muscle enzymes.

Dermatomyositis

Dermatomyositis is a rare inflammatory myopathy with characteristic skin manifestations and muscular weakness. The disease can be categorized as adult idiopathic, juvenile, or amyopathic dermatomyositis as well as that associated with a connective tissue disease or a malignancy. Immunologic factors are most likely involved in the pathogenesis of the disease; however, genetic and environmental issues may also play important roles. Treatment with immunosuppressive agents has proved successful in the majority of patients, although significant morbidity still occurs.

[Immunocytochemical analysis of the inflammatory infiltrate in inclusion body myositis and other neuromuscular disorders with rimmed vacuoles]

Among 1400 muscle biopsies, we found 16 cases with rimmed vacuoles whose diagnosis were sporadic inclusion body myositis (IBM) (4 cases), juvenile spinal muscular atrophy (6 cases), distal myopathies (3 cases), limb-girdle muscular dystrophy (2 cases), and peripheral neuropathy (1 case). Monoclonal antibodies reactive for T lymphocytes and subsets, B lymphocytes, macrophages, natural killer cells, immunoglobulins, and complement were used to analyze the inflammatory infiltrate. The analysis was quantitative and according to the site of accumulation (interstitial, endomysial, and perivascular). The immunocytochemical analysis showed CD8+ lymphocytes in the interstitial in most cases, occasionally inside of muscle fibers, and rarely in the perivascular region. The IBM cases had an increased number of CD8+ lymphocytes comparing with the other diseases. CD8+/CD4+ ratio was increased in IBM compared with the other diseases. Macrophages were frequent in IBM, distal myopathy, and one case of limb-girdle muscular dystrophy. Natural killer cells were frequent at interstitial.

Camptocormia: a case of possible paraneoplastic aetiology

We present a patient with gradual development of camptocormia, three years before a non-Hodgkin's lymphoma was diagnosed. Lymphomas are known to produce neuromuscular symptoms through several indirect mechanisms. Recent studies regard camptocormia as a primary disease of the paravertebral muscles. To our knowledge this is the first report associating camptocormia with malignancy. The possibility of a paraneoplastic syndrome is discussed.

Drug therapy in juvenile dermatomyositis: follow-up study

A series of 33 patients with juvenile dermatomyositis was reviewed in terms of their prognosis in relation to their drug therapy. This retrospective study was intended to help clarify the use of various therapies in this rare, heterogeneous disease from our hospital's experience in the last 24 years. The results confirmed that oral corticosteroids should remain the undisputed first line of treatment. For more refractory, chronic patients, the results suggest that azathioprine should be the favored drug of first choice (in addition to corticosteroids). There may be a role for cyclosporine as a "rescue" treatment, but this needs to be further defined.

Classification and treatment of the juvenile idiopathic inflammatory myopathies

This article reviews the current status of the classification and treatment of the juvenile idiopathic inflammatory myopathies. The intent of classification is to define homogeneous groups that share similar clinical features, disease courses, and responses to therapy. The classification scheme proposed includes clinicopathologic subsets, serologic subjects based on the presence of myositis-specific and myositis-associated autoantibodies, and environmental triggers of myositis. Juvenile dermatomyositis is the most common and widely recognized of these disorders. The second part reviews the history of treatment of juvenile dermatomyositis and discusses agents to consider for patients with refractory disease, unacceptable steroid toxicity, or poor prognostic factors.

Treatment of inflammatory myopathies

The treatment of the immune-mediated inflammatory myopathies remains largely empirical. Corticosteroids are usually effective in polymyositis and dermatomyositis but may need to be combined with methotrexate or azathioprine in some patients. Intravenous immunoglobulin (IVIg) is effective as add-on therapy in some patients not adequately controlled with steroids or immunosuppressive agents, but further controlled trials of IVIg are necessary to define the indications and optimal dose regimens. Cyclophosphamide, cyclosporin, or chlorambucil may be effective in patients with refractory polymyositis or dermatomyositis. Low-dose whole body or lymphoid irradiation is a last option in severely disabled patients resistant to all other treatments. As a small proportion of patients with inclusion body myositis respond to corticosteroid or immunosuppressive therapy, a 3-6-month trial of such therapy is justified in this condition. More specific immunotherapy for these disorders awaits identification of the target antigens and further clarification of the immunopathogenetic mechanisms.

Characteristics of juvenile dermatomyositis in Japan

Questionnaires were sent to 1290 hospitals in Japan asking for data on patients with juvenile dermatomyositis (JDM) diagnosed between June 1984 and May 1994. Of the 204 patients identified by these questionnaires, 102 met the criteria for JDM. JDM is categorized into three subtypes: Banker-type JDM, Brunsting-type and fulminant-type; patients with the latter exhibit markedly elevated serum levels of creatinine phosphokinase (> 10,000 U/mL) and appear to be at risk of renal failure. Cutaneous manifestations were present in 98% of patients and preceded the appearance of other symptoms. This tendency is one of the reasons for the difficulty in some cases in diagnosing the onset of JDM. Better criteria for early treatment of JDM are needed. The results of the present study suggest that itching and calcinosis are factors that indicate a poor prognosis in patients with JDM. Muscle enzyme levels do not always reflect disease activity, suggesting that methods other than measurement of muscle enzymes, such as measurement of the levels of neoprerin and von Willebrand factor antigen, as well as magnetic resonance imaging should be used to be evaluate disease severity. Patients with Brunsting-type JDM who exhibit dysphagia and antinuclear antibody positivity and patients with Banker-type JDM should be treated aggressively. Pulse therapy should be selected as the initial therapy in patients with fulminant-type JDM.

Acute orbital myositis. Case report

The case of 22-year old, white woman with bilateral orbital myositis following an acute upper respiratory tract infection is reported. The most important clinical findings were ocular pain, proptosis, restricted eye motility and swelling of the eyelids. The enlarged eye muscles were seen on orbital computerized tomography scan. The clinical findings of inflammatory orbital myositis and clinical response to corticotherapy are emphasized.

Investigation of muscle disease

Images

Inclusion body myositis: investigation of the mumps virus hypothesis by polymerase chain reaction

Inclusion body myositis (IBM) is a distinctive form of chronic inflammatory myopathy characterized pathologically by the finding of rimmed vacuoles and 15-18nm microtubular filamentous inclusions in muscle fiber nuclei and cytoplasm. The observation that these filaments resembled nucleocapsids of the paramyxovirus group and showed immunoreactivity with mumps virus (MV) antibodies has led to a long-standing postulate that IBM may be a "slow" mumps infection. We searched for the presence of MV RNA in 34 muscle biopsies (17 frozen and 17 paraffin-embedded) from 18 patients with IBM and 43 control biopsies (mainly from patients with other forms of inflammatory myopathy) using a polymerase chain reaction (PCR). The MV PCR was shown to be sensitive and specific for MV strains (including J-L) and the integrity of muscle RNA extracts was confirmed by PCR detection of constitutive Ableson tyrosine kinase mRNA. MV RNA was not found in any biopsy from the IBM group nor any of the control cases. Our results therefore do not support the mumps hypothesis for IBM.

Search for persistent enterovirus infection of muscle in inflammatory myopathies

To investigate the hypothesis that the inflammatory muscle diseases (IMD) polymyositis (PM) and dermatomyositis (DM) may be due to a chronic, persistent enterovirus (EV) infection we sought to determine the prevalence of these viruses in muscle tissue using both nested polymerase chain reaction (PCR) and dot-blot hybridization assays. Thirty-six frozen muscle biopsies from 32 adult cases of IMD and 42 biopsies from 36 control subjects with other neuromuscular disorders were studied. Primers for PCR were chosen to conserved regions of the 5'-untranslated region of the EV genome. Constitutive Ableson tyrosine kinase (ABL) mRNA was detected by PCR to confirm the integrity of muscle RNA extracts. The sensitivity of the EV PCR was determined to be 40-400 copies (12.5-125 ag) of synthetic EV RNA transcript against a background of 1 microgram of cellular RNA. The specificity was assessed using a range of enteroviral and unrelated viral isolates extracted from cell cultures. Of the 78 samples tested, ABL mRNA was successfully detected in all but four samples. The time the biopsies spent in ultracold storage (1-73 months) did not appear to influence the integrity of extracted RNA. When assayed for EV RNA by nested PCR, none of 29 IMD cases (i.e., 28 PM and 1 DM) nor sequential biopsies from 3 PM patients were found to be positive. All 42 control biopsies were also negative for EV RNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Paraneoplastic polymyositis associated with a renal carcinoma

A 56-year-old patient was admitted to hospital because of difficulties in swallowing and in opening his mouth. The serological transaminases were increased. Over the next 6 weeks a bioptically proven polymyositis (more proximally located) caused a respiratory insufficiency which had to be treated by artificial respiration. A tetraplegia connected with a large increase of creatine-kinase was also seen. The general investigations were focused on malign processes with a particular search for bronchial carcinoma. At first a kidney cyst detected by ultrasound but was classified as harmless by several investigators. Finally, a computer tomogram of the abdomen demonstrated a cystic degenerated renal carcinoma, which had been cytologically tested also. The clinical course showed a typical aspect of a paraneoplastic syndrome: after extended nephrectomy a distinct regression of the musculary symptoms developed, but with the development of metastases the symptoms increased again. The interdependence of polymyositis and primary renal carcinoma would appear to be proven.

Inflammatory Myopathy and Walker-Warburg Syndrome: Etiologic Implications

Walker-Warburg syndrome is a well delineated clinical entity with characteristic brain and eye anomalies. Recent diagnostic surveys have revealed that muscular dystrophy is an obligatory feature of this syndome. We report a patient with an inflammatory myopathy that preceded dystrophic changes. While reports of parental consanguinity and multiple affected sibships strongly suggest an autosomal recessive genetic basis for this syndrome, previous pathological analyses of the CNS have suggested an inflammatory process. Our case supports both the notion of an aberrant inflammatory process that is likely under genetic control or etiologic heterogeneity (phenocopies) underlying this syndrome.

Dengue. Muscle biopsy findings in 15 patients

Dengue is known to produce a syndrome involving muscles, tendons and joints. The hallmark of this syndrome is severe myalgia but includes fever, cutaneous rash, and headache. The neuromuscular aspects of this infection are outlined only in isolated reports, and the muscle histopathological features during myalgia have not been described. In order to ascertain the actual neuromuscular involvement in dengue and better comprehend the histological nature of myalgia, we performed a clinical and neurological evaluation, a serum CPK level and a muscle biopsy (with histochemistry) in 15 patients (4 males), median age 23 years (range 14-47) with classic dengue fever, serologically confirmed, during the brazilian dengue epidemics from September 1986 to March 1987. All patients had a history of fever, headache and severe myalgia. Upon examination 4 had a cutaneous rash, 3 had fever, and 3 a small hepatomegaly. The neurological examination was unremarkable in all and included a manual muscle test. CPK was mildly elevated in only 3 patients. Muscle biopsy revealed a light to moderate perivascular mononuclear infiltrate in 12 patients and lipid accumulation in 11. Mild mitochondrial proliferation was seen in 3, few central nuclei in 3, rare foci of myonecrosis in 3, and 2 patients had type grouping. Dengue in our patients, produced myalgia but no detectable muscle weakness or other neuromuscular involvement. The main histopathological correlation with myalgia seems to be a perivascular mononuclear infiltrate and lipid accumulation.

Analysis of T cell receptor repertoire of muscle-infiltrating T lymphocytes in polymyositis. Restricted V alpha/beta rearrangements may indicate antigen-driven selection

Polymyositis is an inflammatory myopathy characterized by mononuclear cell infiltration of muscle tissue. Myocytotoxic T lymphocytes have been recognized in the infiltrates, but the muscle antigen, target of the immune attack, has not been identified. Molecular characterization of the variable regions of T cell receptors (TCRs) on the infiltrating lymphocytes can be expected to provide insights into the pathogenic process. The V alpha/beta TCR repertoire was investigated by RNA-PCR in muscle biopsies from 15 polymyositis patients and 16 controls (6 Duchenne muscular dystrophy and 10 with no inflammatory or dystrophic myopathy). A variety of rearranged variable TCR genes was found in polymyositis, V alpha 1, V alpha 5, V beta 1, and V beta 15 being the most common (present in 60-100% of patients). In Duchenne muscular dystrophy patients TCR V alpha or beta rearrangements were found although no restriction was observed; no rearrangements were found in muscles from the other controls. Sequence analysis revealed the presence of the J beta 2.1 region in 90% of the V beta 15 clones studied, no random N additions in the diversity region, and a common motif within the CDR3 region. These results suggest that selection of muscle-infiltrating T lymphocytes is antigen driven in polymyositis.

Acute neuromuscular respiratory paralysis

Images

Polymyositis with plasma cell infiltrate in essential mixed cryoglobulinaemia

A patient with essential cryoglobulinaemia who presented with polymyositis is described. Muscle biopsy showed intense plasma cell infiltration of muscle. Plasmapheresis produced a rapid resolution of the cutaneous manifestations of the disease, but little improvement in muscle strength. Oral steroids resulted in moderate improvement in muscle strength. There have been no previously reported cases of polymyositis in association with essential cryoglobulinaemia.

Analysis of the outcome of idiopathic inflammatory myopathies with particular emphasis on muscle capillary damage

The objective of this study was to assess the outcome of our series of idiopathic inflammatory myopathies (IIM) with special consideration of capillary damage as a prognostic indicator. We have classified our series of patients with the diagnosis of IIM according to the presence or absence of capillary damage in muscle biopsies, and determined their outcome by means of survival analysis statistical techniques. The follow-up of our patients seems to demonstrate that the patients without capillary damage present a more indolent form of IIM, with a slower response to treatment. The presence of capillary damage indicates a more acute disease, with more morbidity and mortality, but with a faster response to immunosuppression. The presence or absence of capillary damage seems to determine two forms of IIM with differentiated outcome and prognostic.

Benign acute myositis associated with rotavirus gastroenteritis

Acute myositis developed concomitantly with gastroenteritis in a 2-year-old girl. She had temporary pain and swelling of the calf muscles and transient marked elevation of serum creatine kinase values. Rotavirus antigen was detected in stool by latex agglutination, and there was seroconversion of complement-fixation antibody to rotavirus.

Epidemic of acute inflammatory myopathy in Karnataka, south India: 30 cases

Thirty patients of acute inflammatory myopathy were seen over a short period of 11 months (February to December 1986) at NIMHANS, Bangalore, South India. The characteristic features were: short febrile illness followed a few days later by myalgia, edema of extremities, severe motor weakness and involvement of multiple other systems. Their mean age was 32.3 years and M:F ratio was 4:1. CK levels were increased in all. EMG done in 23 patients showed spontaneous activity in 13 and myopathic pattern in all. Nerve conduction studies revealed abnormalities in 12 cases. Muscle biopsy done in 21 patients showed varying degree of myophagocytosis and inflammatory infiltrates. All patients received steroids for only 6-8 weeks. Twenty-two patients recovered, one developed residual disability and 7 patients died during the acute phase. None of the survivors has developed relapse so far. Such cases with monophasic illness in clusters have not been reported earlier.

Juvenile dermatomyositis: a statistical study of 114 patients with dermatomyositis

We conducted a statistical review of 114 cases of dermatomyositis (DMS) treated primarily at the Department of Dermatology at Nagoya University Hospital over 27 years from 1965 to 1991 in order to determine the primary characteristics of juvenile DMS with the following results. 1) Juvenile DMS was found slightly more often in males than females; the male-to-female ratio was 1.4:1. Therefore, unlike adult DMS with its preponderance of females, there was no clear gender predominance. 2) Muscular manifestations tended to follow the appearance of cutaneous manifestations, but the frequency of minor muscular manifestations was high over the entire course of the disease. 3) Laboratory findings showed increases in serum aldolase and serum creatinine kinase with significant frequency when compared with adult patients (p < 0.01 and p < 0.05, respectively). Elevated serum aldolase most often occurred prior to or at the time of the appearance of muscular manifestations, suggesting its usefulness in early diagnosis. The positive rates for the antinuclear antibody on HEp-2 cells and anti-DNA antibody were significantly lower in children than in adults (p < 0.001 and p < 0.05, respectively). 4) There were no cases of juvenile DMS complicated by malignant tumors, interstitial pneumonia, or pulmonary fibrosis. There were also no deaths, and the rate of "remission or improvement" was significantly higher than in adult DMS cases (p < 0.05). Adult cases which remained the same or worsened usually presented with intractable muscular manifestations. In children, however, the cutaneous manifestations were more difficult to treat.(ABSTRACT TRUNCATED AT 250 WORDS)

Microvascular changes in skeletal muscle in idiopathic inflammatory myopathy

Open deltoid muscle biopsy specimens from patients with idiopathic adult dermatomyositis, paraneoplastic dermatomyositis, childhood dermatomyositis, and idiopathic polymyositis, and from control patients were studied. Qualitative and morphometric capillary analysis by phase and electron microscopy was carried out. In the morphologic analysis the most striking difference was the presence of capillary damage and a higher capillary depletion in dermatomyositis as well as a higher capillary density in polymyositis. By electron microscopy, capillaries from patients with dermatomyositis showed mainly microtubuloreticular structures, loss of endothelial plasma membranes, and the appearance of abnormal cytoplasmic organelles. In contrast, capillaries from patients with polymyositis exhibited only minimal changes. By morphometric analysis, muscle capillaries in dermatomyositis had a significantly higher mean endothelial thickness than those in polymyositis. Finally, a significant topographic association between capillary damage and muscle fiber changes was observed only in patients with dermatomyositis. On the other hand, paraneoplastic dermatomyositis showed fewer structural and morphometric capillary changes than the other forms of dermatomyositis. We conclude that dermatomyositis is characterized by microvascular alterations that are absent in polymyositis. The topographic proximity of capillary changes to muscle fiber injury suggests that capillary damage may play a role in the pathogenesis of the muscle lesions observed in patients with dermatomyositis.

Benign acute childhood myositis in Kuwait

Ten children, three girls and seven boys, aged 4-10 years, were admitted with benign acute childhood myositis during spring and winter months (March 1988 to March 1990). They presented with an acute onset of symmetrical calf muscle pain and tenderness, weakness and inability to walk a few days after a flu-like illness. All had raised serum creatine kinase and a normal erythrocyte sedimentation rate, and the majority had low peripheral white blood cell counts with relative lymphocytosis. Serum aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase were found to be raised in four patients. Virological studies performed in six children gave negative results. Full clinical recovery was achieved within 1-7 days. One child developed a second episode. These ten cases of benign acute childhood myositis are the first to be reported from this region.

Muscle siderosis in AIDS: a marker for macrophage dysfunction?

We have observed numerous iron granules in muscle fibres, endothelial cells and macrophages of muscle biopsy specimens of 21 out of 41 AIDS patients with different patterns of muscle involvement. All patients were severely immunodepressed. We report on our findings and discuss the mechanism of muscle siderosis that may point to deterioration of some functions of macrophages at a late stage of HIV infection.

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.

Polymyositis: a case history approach to the differential diagnosis and treatment

A wide range of conditions can mimic polymyositis. Thus, diagnosing this condition can be a challenge. Although no single criterion is diagnostic of polymyositis, the following criteria have been proposed and widely used: (1) symmetric proximal muscle weakness; (2) characteristic violaceous rash on the hands, elbows, and knees; (3) increased muscle enzymes in the serum; (4) characteristic electromyographic findings (insertional activity, fibrillation potentials, motor unit potentials of increased frequency and decreased duration, and normal conduction velocity in nerves); and (5) muscle biopsy specimen with characteristic inflammatory and myopathic changes. Although polymyositis primarily involves muscle, up to 20% of patients may have extramuscular problems. The main treatment for polymyositis is high-dose corticosteroids. In corticosteroid-resistant patients, methotrexate is often effective. In this report, case histories are presented to highlight the usefulness and the limitations of the common diagnostic criteria for polymyositis.

Quantitative electromyography in polymyositis: a reappraisal

Manual analysis of motor unit action potentials (MUAPs) was performed in 33 patients with polymyositis of whom 16 were studied in the acute stage and 17 in the chronic stage. Contrary to common description of "myopathic potentials" as being of low amplitude, short duration, and polyphasic shape, the quantitated study revealed no difference as to amplitude of short duration MUAPs in patients and normal subjects though short-duration MUAP and short duration polyphasic potentials were 4 and 3 times, respectively, more common in patients than in controls. Although the mean duration of MUAPs usually was significantly shorter in polymyositis than in controls, the average scatter of MUAPs duration was the same in the 2 groups. The average incidence of polyphasic MUAPs was 4 times higher in patients than in controls, as was the incidence of those of long duration. To avoid misinterpretation of EMG findings due to an excess of polyphasic MUAPs, a greater number of individual potentials than usually recommended should be collected allowing a valid estimate of the mean duration of MUAPs of simple configuration.

Myopathies associated with hypothyroidism: a review based upon 13 cases

The clinical and myopathological features of 13 patients with a myopathy occurring in association with hypothyroidism are presented. Seven patients had hypothyroid myopathy, including two with the Hoffmann syndrome and one with the Kocher-Debre-Semelaigne syndrome. Five patients had an inflammatory myopathy and one had polymyalgia rheumatica. Serum CK activity was elevated up to 12-fold in the patients with hypothyroid myopathy and returned to normal after treatment with thyroxine. Pathological changes in these cases included type 1 or type 2 fibre atrophy or hypertrophy, myofibre necrosis and regeneration in four cases and, in one case, prominent core-like areas containing amorphous granulo-filamentous material. The findings in this series of cases illustrate the clinical and histopathological heterogeneity of patients with hypothyroid myopathy and the need to consider other myopathies in hypothyroid patients who present with muscular symptoms.