The childhood type of dermatomyositis

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.

Hereditary branching enzyme dysfunction in adult polyglucosan body disease: a possible metabolic cause in two patients

We describe 2 unrelated patients with adult polyglucosan body disease (APBD) diagnosed by sural nerve biopsy. Both patients were offspring of consanguineous marriages. They presented clinically with late onset pyramidal tetraparesis, micturition difficulties, peripheral neuropathy, and mild cognitive impairment. Magnetic resonance imaging of the brain revealed extensive white matter abnormalities in both. In search of a possible metabolic defect, we evaluated glycogen metabolism in these patients and their clinically unaffected children. Branching enzyme activity in the patients' polymorphonuclear leukocytes was about 15% of control values, whereas their children displayed values of 50 to 60%, suggesting a possible autosomal recessive mode of transmission. This is the first report of an inherited metabolic defect in patients with adult polyglucosan body disease. We suggest that branching enzyme dysfunction may be implicated in the pathogenesis of some patients with adult polyglucosan body disease.

Collagen vascular diseases of childhood

This article is devoted to collagen vascular diseases of childhood. The connective tissue diseases that are discussed are lupus erythematosus, scleroderma, and dermatomyositis. Of the vasculitic syndromes, Henoch-Schönlein purpura, acute hemorrhagic edema of infancy, and polyarteritis nodosa are discussed. Although the collagen vascular diseases are rare in the pediatric age group, when they occur they can be very serious.

Polyglucosan body disease

Adult polyglucosan disease has been described in 15 cases. All had signs of peripheral neuropathy, upper motor neuron signs, and 12 of the 15 had sphincter problems. Dementia was prominent in 8 of 15 cases. We reported 2 cases that contained these clinical features. Electrophysiological studies showed axonal neuropathy. Somatosensory evoked potentials on the second patient were abnormal. Sural nerve biopsy showed clusters of polyglucosan bodies. Although the presence of polyglucosan bodies in biopsy is nonspecific, the number as well as the clinical features are necessary to make the diagnosis. Branching enzyme activity in muscle extracts of the muscles were normal. Hence, a specific enzyme abnormality is not yet known.

Microvascular changes in early and advanced dermatomyositis: a quantitative study

In adult dermatomyositis 10 muscle specimens with no or minimal histological alterations were compared with 7 that showed typical alterations. Five specimens from patients with inclusion body myositis, 5 from patients with polymyositis, and 8 from normal subjects served as controls. Vascular endothelium, visualized with the lectin Ulex europaeus agglutinin I, and complement membrane attack complex were demonstrated in the same cryostat sections by paired immunofluorescence. Large randomly selected fields were analyzed to determine the number of capillaries per square millimeter of fiber area (capillary density), per 1,000-microns 2 area of each muscle fiber (capillary index), and in 100 x 100-microns grid squares. In dermatomyositis specimens with minimal structural alterations there was focal capillary depletion, the capillary density was significantly reduced, and the frequency distributions of the capillary index and grid count were shifted to the left. In advanced dermatomyositis specimens, the findings were similar but more severe. In both kinds of specimens, clusters of capillaries reacted for complement membrane attack complex. The 2 patients with the highest proportion of vessels positive for membrane attack complex had a fulminant and fatal course. In polymyositis and inclusion body myositis specimens, the capillaries had a normal overall density and none reacted for membrane attack complex. The findings imply that the capillaries are an early and specific target of the disease process in dermatomyositis.

Relationship between capillary and muscle damage in dermatomyositis

To assess the pathogenetic importance of capillary damage and its relationship with degenerating muscle fibers in dermatomyositis (DM), an electron microscope study of eight muscle biopsy specimens (adult and juvenile forms) and seven muscle specimens from patients with other neuromuscular diseases was conducted. There was a 49% reduction of capillaries in the muscle specimens of DM patients. Capillary damage also was more frequent in the DM group than in control group (p less than 0.001). We found a striking relation between capillary and muscle damage in the DM group (p less than 0.002) but not in the control group. The diagnostic value of undulating tubules within endothelial cells is also discussed.

Tubuloreticular structures (TRS) and cylindric confronting cisternae (CCC) in childhood dermatomyositis

Tubuloreticular structures (TRS) and cylindric confronting cisternae (CCC) have been observed in circulating lymphocytes and in the muscle of six children with dermatomyositis. The presence of TRS was seen in all cases investigated, the number of CCC increased in various cells with the severity of the disease. Extensive formation of TRS and CCC in childhood dermatomyositis probably reflects local or systemic alpha-interferon production and suggests that some viral factor is responsible for the disease.

Early ultrastructural alterations in adult dermatomyositis. Capillary abnormalities precede other structural changes in muscle

In 6 adults with dermatomyositis, minimally weak or nonweak muscles that showed inconclusive light-microscopic alterations were examined by electron microscopy. In all 6 specimens, this revealed pathologic changes in endomysial capillaries. The endothelial cells harbored microtubular inclusions and microvacuoles in all cases; pale swollen endothelial cells were observed in 3 specimens. There were no significant ultrastructural changes in the muscle fibers. In all cases, a small proportion of muscle capillaries were immunoreactive for complement membrane attack complex neoantigens. The findings imply that in adult dermatomyositis capillary injury precedes muscle fiber damage and infiltration by inflammatory cells, and that the microvasculature is an early and specific target of the disease process in muscle.

Polyglucosan bodies in intramuscular motor nerves

The presence of polyglucosan bodies was studied in intramuscular motor nerves of 292 muscle biopsies. These biopsies were classified into five diagnostic categories and investigated for the presence of polyglucosan bodies in relation to age and sex. Their presence was nonspecific in patients over 20 years, the only correlation being with ageing. Under 20 years, their presence pointed to the diagnosis of Lafora's disease. In cases in which both a muscle biopsy and a sural nerve biopsy were performed, the former appeared to contain these polyglucosans more frequently.

Perifascicular atrophic fibers in childhood dermatomyositis with particular reference to mitochondrial changes

Ten of 17 muscle biopsy specimens from 15 patients with childhood dermatomyositis (DM) showed distinct perifascicular atrophy. The atrophic fibers showed the following characteristics: (1) decreased cytochrome c oxidase (CCO) activity, (2) rare positive reaction with acridine orange (AO) staining, (3) type 2C reaction in 7.9% (0.4-17.5%) of the fibers, (4) an increased number of activated satellite cells, (5) mitochondria which were increased in number but decreased in size, (6) a significantly decreased CCO activity in isolated mitochondria (51.6 +/- 30.3 nmol/min per mg mitochondrial protein) as compared with that in the controls (103.6 +/- 41.5). The major pathogenetic mechanism in muscles in childhood DM is thought to be ischemia due to involvement of the microvasculature. The presence of type 2C fibers and increased numbers of activated satellite cells reflect a focal repair process taking place concomitantly in the damaged myofibers. Mitochondrial enzyme defect, especially CCO deficiency is present not only in genetic disorders with mitochondrial involvement but in other neuromuscular disorders including inflammatory myopathies.

Neuromuscular histopathology in (New Zealand black x New Zealand white)F1 and MRL-lpr/lpr autoimmune mice: models for skeletal muscle involvement in connective tissue disease

Skeletal muscle from (New Zealand black x New Zealand white)F1 and MRL-lpr/lpr mice was examined for histopathologic abnormalities. Although young animals had no muscle abnormalities, older mice in both strains had the following histopathologic abnormalities: perimysial/endomysial inflammation, acute simple denervation, muscle degeneration/necrosis, and an increase in internal nuclei. MRL-lpr/lpr mice had the following additional histopathologic abnormalities: inflammatory vascular disease (vasculitis), central myofibrillar loss, fascial inflammation, and tubular aggregates. These abnormalities are comparable with those seen in human connective tissue diseases, particularly the association with inflammation. These mouse strains provide good animal models for the study of immunopathologic processes of skeletal muscle associated with connective tissue disease.

C4 complement allotypes in juvenile dermatomyositis

Twenty probands with juvenile dermatomyositis and their relatives were studied to determine the inherited segregation patterns of class I, II, and III HLA region markers including C4A, C4B, Bf, and C2 complement polymorphisms. The extended haplotype B8, DR3, C4A*Q0, C4B*1, C2*C, and Bf*S was present in 13 of the 20 probands. Three other probands also carried a haplotype with a null allele for C4A and two further probands carried a null allele for C4B; only two probands had no detectable C4 null allele. These data confirm previous studies showing high frequencies of B8 and DR3 in patients with juvenile dermatomyositis, but show that there is a higher association with null alleles of C4. This suggests that the C4 genes are either themselves the disease-susceptibility genes or are in very strong linkage disequilibrium with such genes.

Childhood polymyositis/dermatomyositis

Children with PM/DM differ in many respects from adults with PM/DM. The most characteristic and distinctive feature is the presence of a widespread vasculopathy. Although the pathogenesis is unknown, roles for both humoral and cell-mediated immunity have been proposed. Most intriguing is the evidence for a viral agent that is capable of precipitating an ongoing, immunologically mediated reaction damaging muscles and endothelial cells. Much remains to be discovered, however, regarding the pathogenesis of this disease.

Characterization of mononuclear exudates in idiopathic inflammatory myopathies

Percentages of B-cells, T-cells and subsets Th, Ts, T activated, and macrophages were analyzed by using monoclonal antibodies in a series of 24 patients [19 dermatomyosis (DM) and 5 polymyositis (PM)]. Specific site of deposition of these cells was also identified (endomysial, perimysial and perivascular). We were able to find a greater number of endomysial T-cells in PM than in DM. However, B-cells were more frequent at perivascular sites in DM than in PM. These findings support the previous reported hypothesis that humorally-mediated immune damage in both vascular and muscle cells predominates in DM while cellular cytotoxic mediated damage is more marked in PM patients.

Spatial distribution of muscle necrosis in biopsies from patients with inflammatory muscle disorders

Muscle biopsies from 56 patients with polymyositis (PM), juvenile dermatomyositis (JDM) and adult dermatomyositis (ADM) were investigated using a range of quantitative histological techniques. The objective was to present data on the extent and distribution of muscle fibre degeneration in these patients and to determine whether these data were compatible with postulated mechanisms of fibre injury. Atrophy of one or more of the major fibre types was found in 45/56 biopsies but there was no evidence that particular patterns of type-specific atrophy were characteristic of any individual disease group. However, selective atrophy and/or necrosis of perifascicular fibres was much more common in JDM patients than in ADM or PM groups. In virtually all biopsies where abnormalities of the microvasculature were apparent (7/8 JDM biopsies, 4/13 ADM biopsies and 5/33 PM biopsies) the distribution of acute muscle necrosis was found to be non-random (clustered). However, a substantial proportion of biopsies in the PM group showed clustering of necrotic fibres in the absence of evidence of vascular involvement. This finding suggests that non-random targetting of muscle fibres by effector cells may occur.

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.

Activation of complement and coagulation in juvenile dermatomyositis

In patients with juvenile dermatomyositis (JDM), small vessel occlusion and thrombosis result in a decrease in the capillary: muscle fiber ratio. We studied 15 patients with JDM. Six of 7 patients with clinically active JDM had elevated levels of C3d. Moreover, concentrations of fibrinopeptide A and factor VIII-related antigen were significantly increased in patients with clinically active JDM.

Classification of myositis. Correlations between morphological and clinical classifications of inflammatory muscle disease

Insufficient clinical data given to pathologists often hamper the differentiation of inflammatory muscle diseases. Thus we proved the value of a classification based only upon morphological criteria. Among 160 biopsies with myositic pattern (4.9% of a series of 3264 muscle biopsies) we could distinguish the following groups: Interstitial inflammation with only few fibre necroses (17.6%), predominance of fibre necroses with few inflammatory infiltrates (38.1%), small vessel vasculitis (20.0%), arteritis (13.1%), granulomatous myositis (8.8%) and polymorphonuclear leukocytic infiltrates (2.6%). This classification is compared with the used clinical diagnoses. Some special morphological aspects (histometric and immunocytologic examinations, tissue calcification, inclusion bodies, neurogenic atrophies) are analysed and so are some clinical peculiarities (e.g. malignoma-association, differentiation of mixed connective tissue syndrome, drug-induced reactions). The diagnostic value of purely morphologic criteria is restricted. For better diagnostic work a great number of clinical informations is required. Nevertheless, certain morphological patterns give important directions, e.g. to occult malignoma.

Juvenile dermatomyositis induced by toxoplasmosis

A 10-year-old girl from southern Alberta, Canada, who had close contact with cats, developed typical features of dermatomyositis. The diagnosis was confirmed by muscle biopsy. A toxoplasmosis titer was 1:16,384 by indirect fluorescent antibody technique, and the IgM response to toxoplasma was positive. Only minimal improvement followed prednisone and azathioprine administration, but she rapidly improved after 4 weeks of treatment for toxoplasmosis with pyrimethamine and sulfadiazine. A year after the onset of dermatomyositis, she showed no weakness or cutaneous lesions, and a repeat muscle biopsy no longer showed inflammation, perifascicular atrophy, or regeneration of myofibers. She remains asymptomatic more than 2 years after discontinuation of all medications. Investigation for immune deficiency disease 1 year after therapy revealed that lymphocytic response to T-cell and B-cell mitogens was normal, as were immunoglobulin and complement levels. She had mild impairment of natural killer cell activity and a positive antinuclear factor. Her rapid improvement on specific therapy and lack of significant long-term immune deficiency is consistent with acute toxoplasmosis infection in an immunologically competent child.

Juvenile dermatomyositis

Myositis in childhood is characterized by elevated serum levels of muscle-derived enzymes, proximal symmetrical muscle weakness, abnormal EMG findings, and a muscle biopsy, which frequently documents an inflammatory process. In the pediatric age group, JDMS, which has characteristic cutaneous involvement in addition to myositis, is much more common than PM and is more common among female patients. With the use of steroids, mortality has been reduced from 33 per cent to 7 per cent. The development of calcifications can be the most debilitating consequence of JDMS. It is our premise that JDMS is a distinct disease entity and that the increase in HLA-B8 and DR3 in JDMS suggests that genetic background may predispose to disease development. There are conflicting data concerning immunologic abnormalities in JDMS, but there appears to be impairment of natural killing and evidence of complement activation. Results of tests for ANA frequently are positive in JDMS, but Jo-1 antibody, found in some adults with PM, has not been found in JDMS. Most newly diagnosed JDMS patients have antibodies to coxsackie B that may be related to the pathogenesis of this disease. Specific pathologic findings of endothelial cells containing reticulotubular inclusions are associated with small vessel occlusion, subsequent obliteration, and increased factor VIII levels in clinically active disease. In addition to physical therapy, steroids are used most frequently, but other immunosuppressive agents and plasmapheresis have been tried in severely ill children. Rigorous evaluation of the efficacy of these modalities is needed.

Mononuclear cells in myopathies: quantitation of functionally distinct subsets, recognition of antigen-specific cell-mediated cytotoxicity in some diseases, and implications for the pathogenesis of the different inflammatory myopathies

Monoclonal antibodies reactive for B cells, T cells, T-cell subsets, killer (K) and natural killer (NK) cells, and the Ia antigen were used to analyze mononuclear cell subsets in scleroderma (SD), dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM), Duchenne dystrophy (DD), and normal muscle. The analysis, which was quantitative, was performed according to diagnosis and site of accumulation. Cells at perivascular, perimysial, and endomysial sites of accumulation, and cells focally surrounding and invading nonnecrotic muscle fibers, were analyzed separately. Individual antigens were localized in 2-micron serial sections, or multiple antigens were demonstrated in a given section by sequential paired immunofluorescence. The latter approach allowed the identification of the cell phenotypes in which functional properties are defined by multiple markers, e.g., T8+ and T4+ cells that are either activated or not activated, T8+ cells that are either cytotoxic or suppressor T cells, and K/NK cells of varying maturity and killing capability. The interactions of inflammatory cells of various types with each other and the muscle fiber were further investigated by immunoelectron microscopy. In SD, the findings provide evidence for a cell-mediated immune effector response against a connective tissue and/or vascular element. In DM, the effector response appears to be predominantly humoral. In PM and IBM (but not in DM or SD), there is invasion and destruction of nonnecrotic muscle fibers by cytotoxic T cells, with or without accompanying macrophages. Because T-cell-mediated injury is antigen- and major histocompatibility complex-restricted, clones of T cells must have been sensitized previously to a muscle fiber-associated surface antigen. The identity of the putative antigen(s) remains an important, unsolved question.

Distribution of capillaries in normal and diseased human skeletal muscle

The distribution of capillaries was studied in muscle biopsies in a large number of normal subjects and in patients with disuse atrophy, inflammatory myopathies, and other chronic myopathic and neurogenic disorders. The cryostat retrieval technique was used, along with capillary and muscle fiber morphometry, to quantitate capillary distribution around specific fiber types. In all diseased and normal muscle, the number of capillaries per fiber (C/F) and the number of capillaries surrounding a fiber (CAF) increased with fiber diameter. More capillaries typically surrounded type 1 than type 2 fibers within a given group. When all inflammatory myopathy patients (polymyositis, dermatomyositis, and polymyositis plus second connective tissue disease) were compared with normal adults, their muscle biopsies had fewer capillaries per fiber over the same diameter range. The numerous variables influencing capillary number in normal and diseased muscle are discussed.

Microvascular deposition of complement membrane attack complex in dermatomyositis

We examined the role of the complement system in the pathogenesis of dermatomyositis. Using an antibody against the neoantigens of the terminal C5b-9 membrane attack complex, we performed immunocytochemical studies that localized this complex to the intramuscular microvasculature (arterioles and capillaries) of muscle biopsy specimens from 10 of 12 patients (83 percent) with childhood dermatomyositis and 5 of 19 patients (26 percent) with adult dermatomyositis. Fifty-two control specimens, including 14 from patients with polymyositis and 12 from patients with denervation atrophy (a condition known to be associated with necrotic capillaries), showed no deposition of membrane attack complex in the microvasculature. These findings indicate that the complement system is deposited, bound, and activated to completion within the intramuscular microvasculature of patients with dermatomyositis. In addition to providing further evidence for the presence of vasculopathy in dermatomyositis, these findings suggest a primary role for complement in mediating vessel injury in the disease, particularly in its childhood form.

Ultrastructural abnormalities in muscular vessels of hyperthyroid patients

An electron microscope study of needle biopsies from the quadriceps muscle was carried out in 11 non-selected patients (ten females and one male), with clinically and laboratory-diagnosed hyperthyroid disease. Alterations of the normal structure of muscle fibres were found in all cases. Changes in capillaries were found in ten patients, and ranged from an increase in basement membrane thickness with reduplication, to total destruction of the capillaries. The importance of the vascular involvement in the muscles of patients with Graves-Basedow disease is stressed.

Structural alterations of the intramuscular nerves and junctional region in extraocular muscles of C57BL/Ks (db/db) diabetic mice

The extraocular muscles of the C57BL/Ks (db/db) diabetic mutant mouse were examined by electron microscopy. The intramuscular myelinated nerves and the junctional apparatus of the singly and multiply innervated muscle fibers were found to exhibit various anomalies. Lamellated inclusion bodies were found in many of the Schwann cells of the myelinated nerve fibers; intra-axonal inclusion bodies resembling polyglucosan bodies were also observed. Junctional abnormalities consisted of various types of inclusion bodies within the junctional sarcoplasm and within sole-plate nuclei; in addition, hypertrophied endplates were observed and often penetrated by networks of axonal terminal branches. At times, pseudopod-like extensions of the junctional sarcoplasm encompassed and made protracted synaptic contacts with the incoming axons.

Recent advances in the morphology of myositis

Myositis in man may be divided into infectious and non-infectious forms. The myopathologist more often deals with the latter forms which comprise dermatomyositis/polymyositis, inclusion body myositis, mixed connective tissue disease/collagenoses, and granulomatous myopathies. Modern morphological techniques as enzyme-histochemistry, electron microscopy, immunohistology, and morphometry are of different value in various forms of myositis, but are often indispensable techniques in up-to-date diagnostic work up of a myositis.

Potassium depletion myopathy: a clinical and morphological study of six cases

Acute myopathy in conditions associated with endogenous or drug-induced potassium loss has been reported. We describe six patients with potassium depletion myopathy (P-DM). The clinical picture included flaccid muscle weakness without sensory loss, myalgia, polyuria, and polydipsia. All the cases had markedly increased serum creatine kinase (CK) levels. The most consistent pathological characteristics were phagocytosis of degenerating muscle fibers plus fiber regeneration. Atrophy of type 2 fibers was observed. Vacuoles and vesicular elements originating from T-tubules were also encountered. The clinical manifestations and morphological changes had reversed after potassium repletion. Both constriction of vascular smooth muscle and cellular energy failure may be pathogenetic factors in P-DM.

Polyglucosan bodies in the sural nerve of a diabetic patient with polyneuropathy

In the sural nerve of a 62-year-old woman with impaired glucose tolerance test and polyneuropathy, many intra-axonal polyglucosan bodies were observed. Polyglucosan bodies have been described in spontaneously or alloxan-diabetic rats, but are not usually observed in human diabetic neuropathy. Since intra-axonal polyglucosan bodies can occur in the sural nerve in various diseases and in aging, they are considered as non-specific changes. Their presence is probably related to a primary axonal neuropathy.

Familial myopathies with restricted distribution, facial weakness and inflammatory changes in affected muscles

A myopathy characterized by restricted involvement of few muscles and inflammatory cell infiltration was observed in three families. In the first family, clinical features, hereditary transmission and biopsy findings were consistent with the diagnosis of facioscapulohumeral dystrophy. However in three of the four affected members, the occurrence of atrophies was specifically initiated by severe muscular pain. In the second family two 8-year-old identical twins had both marked facial weakness and atrophy limited to the right quadriceps femoris. In the third family, marked asymmetry of muscular wasting in the upper limbs was found in the 17-year-old daughter of a man suffering from facial and axial weakness. The indication of corticotherapy in such cases is discussed.

Morphometric approaches to perifascicular atrophy in muscle biopsy: do they help to diagnose polymyositis?

The sizes of muscle fibres in the peripheral and central parts of fascicles were compared in biopsies from patients with polymyositis/dermatomyositis, patients with slowly progressing muscular dystrophies and normal controls. Of three quantitative parameters tested, perifascicular atrophy factor gave the best discrimination between the patient groups. This factor is obtained by subtracting the atrophy factor of the peripheral fibres from that of the central ones. In polymyositis, the values tend to be negative as a result of atrophy affecting selectively the peripheral fibres, whereas in dystrophies the values are usually close to zero or positive. For the comparison between polymyositis and muscular dystrophy, the test based on perifascicular atrophy factor has an estimated sensitivity of 83% and a specificity of 65%. This quantitative method is thus able to increase sensitivity of the diagnosis of polymyositis over that attained by the subjective evaluation, even at the cost of a sizeable false-positive rate.

Painful lumbosacral plexopathy with elevated erythrocyte sedimentation rate: a treatable inflammatory syndrome

Six patients had a syndrome of painful lumbosacral plexopathy and elevated erythrocyte sedimentation rate. Sural nerve biopsy in each case showed axonal degeneration and epineurial arterioles surrounded by mononuclear inflammatory cells. Differential fascicular involvement suggested an ischemic cause in three nerves, but no patient had a necrotizing vasculitis. None of the six patients had vasculitis or cancer. Three of the six were diabetic and were initially thought to have diabetic plexopathy, but deterioration continued despite control of the diabetes. These six patients appeared to have an ischemic neuropathy with an immunological basis. Five were treated with immunosuppressant drugs, and in four the plexopathy improved or was arrested. The pathogenesis is unclear, but postmortem findings in one case suggest that the syndrome does not stem from an underlying vasculitis.

Duodenal perforation in childhood dermatomyositis

Perforation of the duodenum is an uncommon, but serious complication which may occur in children with dermatomyositis. In this disease vasculitis may involve the bowel to a variable extent and result in radiologic manifestations of intestinal injury ranging from benign pneumatosis intestinalis to signs of bowel perforation. We report two children with dermatomyositis in whom perforation of the second portion of the duodenum occurred. This serious complication should be considered in any child with dermatomyositis when extraluminal gas is suspected on abdominal radiographs.

The inflammatory myopathies

Images

Dermatomyositis and multiple malignancies in a patient treated with methotrexate

Dermatomyositis (DM) has been linked to internal malignancy but this relationship is quite variable in respect to tumor type and time sequence. The occurrence of multiple cancers in an individual with DM is rare. Immunosuppressive agents, particularly methotrexate have been used increasingly in corticosteroid resistant cases or for their corticosteroid sparing effects. These agents have not been implicated in the development of malignancy in patients with DM. A patient with a uterine adenocarcinoma developed DM that despite tumor removal was not responsive to corticosteroids. She was successfully treated with methotrexate for 18 months. She has subsequently developed an adenocarcinoma of the breast. The relationship of malignancy and DM as well as the role of methotrexate in the development of the second primary will be discussed.

Localized nodular myositis and the diagnosis of the localized muscle mass

Localized nodular myositis (LNM) is a rare variant of polymyositis beginning with inflammatory nodules within muscles. Only seven cases have so far been reported in the literature. We describe a probable further case of LNM in a 67-year-old man with ischemic claudication of the left leg for three years who presented with painful nodules in the left gastrocnemius muscle and signs of systemic disease; a complete follow-up was not possible, because the patient died after only two months and autopsy was not performed. Muscle biopsy showed localized areas of necrotic and inflammatory pleomorphic changes, in keeping with the features of the other known cases. The ultrastructural findings (not previously reported in this disease) were characterized by marked changes of endomysial capillaries, with fibroblastic metamorphosis of the endothelial cells, and by the presence of filamentous inclusions in the myonuclei. The differential diagnosis of LNM from other localized muscle masses, chiefly from muscle infarct, is discussed.

Skeletal muscle immunopathology

The inflammatory myopathies are a heterogeneous group of diseases currently categorized by clinical findings, laboratory data, and routine histopathologic features. In the ten years since the direct immunofluorescent (DIF) findings in idiopathic inflammatory myopathy were described, there have been a variety of series reporting DIF findings in various rheumatic and non-rheumatic diseases. This paper reviews this experience and attempts to relate the observations to immunologic mechanisms applicable to skeletal muscle. The potential contributions of direct immunohistochemical methodologies have yet to be realized, because 1) there is a paucity of data actually correlating these findings to clinicopathologic data in patients and experimental models and 2) these techniques have been limited to probing for the humoral response. The future expanded use of this technique should include histochemically tagged antisera to T-lymphocyte antigens, macrophages, biologic modifiers, and suspected etiologic agents.

Inflammatory myopathy: a review of etiologic and pathogenetic factors

Human idiopathic inflammatory myopathy is an acquired disorder with an annual incidence of two to five cases per million. A genetic influence on host susceptibility may also play a role. With the marked heterogeneity of the disease one of the major challenges is to identify subsets that might share a more uniform pathogenesis and manifest a less diverse profile of clinical findings, histopathological abnormalities, and natural history. Dermatomyositis can be distinguished by clinical appearance and pathological changes, but the recognition of additional disease subsets remains very inexact. Current evidence suggests that dermatomyositis occurs as a result of a vasculopathy, but immune mechanisms involved in other categories of idiopathic inflammatory myopathy may also involve cell-mediated immunity and possibly multiple mechanisms. Even though viral-induced muscle inflammation occurs in humans, there is no convincing evidence for a viral cause of idiopathic inflammatory myopathy. Experimental allergic myositis may be produced by the injection of animals with skeletal muscle homogenates and complete Freund's adjuvant, but the myositogenic factor is unknown and the parallels between experimental allergic myositis and human idiopathic inflammatory myopathy are limited.

A search for genetic influence in idiopathic inflammatory myopathy

33 patients with idiopathic inflammatory myopathies (polymyositis or dermatomyositis) and 45 of their first-degree relatives were investigated in a search for any influence of genetic factors in these diseases. None of the relatives had evidence of an inflammatory myopathy but 13 had some other autoimmune disease. Mean serum IgG levels were reduced and serum C3c concentration increased both in patients and relatives. Levels of IgM were reduced and C4 increased in some groups of patients. The incidence of autoantibodies was increased in the patient group, particularly in those with isolated dermatomyositis or other systemic features, but not in the relatives. HLA, blood group and other genetic markers showed no deviation from normal population frequencies. Evidence favouring a genetic influence on the etiology of idiopathic inflammatory myopathy is restricted to disturbance of levels of some Ig and complement components, and for these there may be other explanations.

Childhood type polymyositis and rapidly progressive glomerulonephritis

A 21-year-old women developed rapid muscle weakness and quickly deteriorating renal function. Pathological findings revealed prominent vasculitis in the muscle and crescentic glomerulonephritis. Combined steroid and heparin treatments could not prevent the development of the renal lesion, but the muscle involvement had soon improved. Although the pathogenesis remains unclear, immune complexes may be involved in this renal lesion.