The Brazilian Society of Rheumatology recommendations on investigation and diagnosis of systemic autoimmune myopathies

High prevalence of necrotizing myofibers in adult dermatomyositis muscle biopsies

INTRODUCTION/OBJECTIVES

This study aimed to analyze the presence, grade, and relevance of myofiber necrosis in the muscle tissues of patients with adult dermatomyositis. Second, these parameters were associated with the patients' demographic, clinical, and laboratory data.

METHOD

This was a retrospective study, from 2001 to 2021, which included 89 muscle biopsies of patients with definite dermatomyositis performed at the time of diagnostic investigation. Immunohistochemical analysis was performed on serially frozen muscle sections. The presence and degree of endomysial/perifascicular myofiber necrosis were also analyzed. The degree of necrosis was semi-quantitatively coded as absent/mild, moderate, or severe. The presence or absence of perifascicular atrophy and also perivascular lymphomononuclear infiltration was also evaluated.

RESULTS

Muscle biopsies from 89 patients, the majority of whom were Caucasian women, were evaluated. Both perifascicular atrophy and perivascular lymphomononuclear infiltrates were observed in 76 (85.4%) samples. Moderate or intense areas of myofiber necrosis in endomysial/perifascicular areas were found in 30/89 (33.7%) and 14/89 (15.7%) muscle biopsies, respectively, with a predominance of macrophagic infiltrate in relation to lymphomononuclear cells in these regions. The degree of muscle weakness in the limbs (upper and lower) was associated only with areas of intense myofiber necrosis.

CONCLUSIONS

A high prevalence of myofiber necrosis was observed, which patients resembled the initial clinical feature of patients with immune-mediated necrotizing myopathies. Key Point • A high prevalence of myofiber necrosis was observed in muscle biopsies of patients with dermatomyositis.

Long-term effects of early pulse methylprednisolone and intravenous immunoglobulin in patients with dermatomyositis and polymyositis

OBJECTIVE

To evaluate the long-term effects of pulse intravenous methylprednisolone (IVMP) or intravenous immunoglobulin (IVIG) administered during the first year of diagnosis in dermatomyositis (DM) and polymyositis (PM) patients.

METHODS

This is a retrospective single-center cohort study of patients with DM/PM followed for up to 4 years from 2001 to 2017. We used Cox regression models to estimate hazard ratios (HRs) and assess the effects of early pulse IVMP or IVIG on 3 outcomes: complete clinical response, corticosteroid discontinuation, and survival. Analysis was adjusted for clinical, laboratory, and treatment covariates.

RESULTS

A total of 204 patients were included and categorized into 4 initial treatment groups: pulse IVMP (n = 46), pulse IVMP+IVIG (n = 55), IVIG (n = 10), and without IVMP or IVIG (n = 93). The groups of early pulse IVMP and pulse IVMP+IVIG had a higher HR for complete clinical response in the multivariate models (HR = 1.56, 95% CI = 1.05-2.33, p = 0.029; and HR = 1.58, 95% CI = 1.02-2.45, p = 0.041, respectively). Only the group of pulse IVMP+IVIG had a significant association with corticosteroid discontinuation in the multivariate analysis (HR = 1.65, 95% CI = 1.02-2.68, p = 0.043). Early pulse IVMP or IVIG had no impact on mortality.

CONCLUSION

Despite having a more severe disease profile, patients with DM/PM submitted to pulse IVMP or pulse IVMP+IVIG during the first year of diagnosis had a higher HR for complete clinical response, whereas the combination of pulse IVMP+IVIG had an association with corticosteroid discontinuation. Prospective long-term studies are warranted to confirm these benefits of early pulse IVMP and IVIG on patients with DM/PM.