Myositis with endomysial cell invasion indicates inclusion body myositis even if other criteria are not fulfilled.

The objective of this study was to investigate if patients with endomysial mononuclear cell infiltrates invading non-necrotic fibers have a disease course consistent with inclusion body myositis (IBM), irrespective of other histopathological and clinical characteristics. All patients with a muscle biopsy showing endomysial inflammation with invasion of non-necrotic muscle fibers during the period 1979-2006 in two tertiary neuromuscular referral centers were classified into three groups: 1) patients whose biopsies also showed rimmed vacuoles; 2) patients whose biopsies showed no vacuoles but fulfilled clinical criteria for IBM, and 3) patients whose biopsies showed no vacuoles, and also did not fulfill clinical criteria for IBM (unclassified patients). These groups were compared with regard to age, gender, clinical features, and disease course including response to immunosuppressive treatment. Eighty-one individuals (41 men) were included. Rimmed vacuoles were found in 49 patients (60.5%). Fourteen patients (17.3%) fulfilled clinical criteria for IBM and 18 patients (22.2%) were unclassified at presentation. At follow up (mean duration 9 years) three women remained unclassified (4%). There were no differences in disease course or effect of treatment between the three groups. Men had more often rimmed vacuoles than women (73% vs 48%; p = 0.018), and women more often than men were unclassified. Women tended to show more often temporary improvement if treated (p = 0.07), but none had sustained improvement. In conclusion, patients with a muscle biopsy showing endomysial cell infiltration with invasion of non-necrotic muscle fibers most probably have IBM, regardless of clinical and other pathological features. Women lack typical features more often than men.

Oral dexamethasone pulse therapy versus daily prednisolone in sub-acute onset myositis, a randomised clinical trial.

To determine if high-dose pulsed dexamethasone is more effective and safer than daily high-dose prednisolone in treatment-naive adult patients with inflammatory myopathies (sporadic inclusion body myositis excluded) we performed a multicenter, double-blind randomised controlled clinical trial with 18 months follow-up. Sixty-two patients were randomised into 28-day cycles of oral high-dose dexamethasone or daily high-dose prednisolone. Primary outcome measures included (1) seven point composite score of six clinically relevant outcomes and (2) (time-to) remission and (time-to) relapse. No difference between both treatment groups on the composite score was found. Side-effects occurred significantly less frequently in the dexamethasone group. Median time to relapse was 60 (2.9) weeks in the prednisolone and 44 (4.7) weeks in the dexamethasone group (log-rank test p=0.03). In conclusion, pulsed high-dose oral dexamethasone is not superior to daily prednisolone as first-line treatment of idiopathic inflammatory myopathies, but is a good alternative by causing substantially fewer side-effects.

Association of the leukocyte immunoglobulin G (Fcgamma) receptor IIIa-158V/F polymorphism with inflammatory myopathies in Dutch patients.

Leukocytes are involved in the pathogenesis of idiopathic inflammatory myopathies (IIMs). Immunoglobulin G (IgG) receptors (FcgammaR) link the specificity of IgG to the effector functions of leukocytes. Several FcgammaR subclasses display functional polymorphisms that determine in part the vigour of the inflammatory response. FcgammaRIIIa genotypes were differentially distributed among 100 IIM patients compared with 514 healthy controls with a significant increase of the homozygous FcgammaRIIIa-V-158 genotype (3 x 2 contingency table, chi(2) = 6.3, P = 0.04). Odds ratios (ORs) increased at the addition of each FcgammaRIIIa-V-158 allele, in particular among patients with non-specific myositis and dermatomyositis {OR 2.1 [95% confidence interval (CI) 1.1-4.3] and 2.7 (95% CI 1.1-6.4) for FcgammaRIIIa-V/F158 and FcgammaRIIIa-V/V158 genotypes, respectively, using FcgammaRIIIa-F/F158 as a reference group}. These data suggest that the FcgammaRIIIa-V-158 allele may constitute a genetic risk marker for IIM.

Spontaneous recovery of dermatomyositis and unspecified myositis in three adult patients.

Dermatomyositis (DM), polymyositis and unspecified myositis are idiopathic inflammatory myopathies in which prednisone is usually started as soon as the diagnosis has been established. Therefore, little is known about the natural history of these diseases and spontaneous recovery may escape attention. Here, we present three patients who achieved remission without administration of immunosuppressants. In these three patients, treatment was not started because of spontaneously improving symptoms and signs during the diagnostic process. After 3-5 years, all patients are still free of muscle weakness. These case reports demonstrate that spontaneous long lasting remission can occur in a small proportion of patients with subacute onset idiopathic inflammatory myopathies. In some patients, immunosuppressive treatment with the risk of serious side effects can perhaps be omitted. However, close and frequent monitoring is required in these instances.