Idiopathic inflammatory myopathies overlapping with systemic diseases

Abstract

A muscle biopsy is currently requested to assess the diagnosis of an idiopathic inflammatory myopathy overlapping with a systemic disease. During the past few years, the classification of inflammatory myopathy subtypes has been revisited progressively on the basis of correlations between clinical phenotypes, autoantibodies and histological data. Several syndromic entities are now more clearly defined, and the aim of the present review is to clarify the contribution of muscle biopsy in a setting of idiopathic inflammatory myopathies overlapping with systemic diseases. .

Figure 1.. A, B: Muscle biopsy of a patient harboring both anti-PM/Scl and anti-Ku autoantibodies. This 60-year-old Caucasian man suffered from an overlap syndrome with myositis, systemic sclerosis, interstitial lung disease, and Raynaud phenomenon. Hematoxylin-stained frozen section (A) shows variations in myofiber sizes with a few regenerating fibers and mild endomysial lymphocytic infiltration. MHC class I immunostaining (B) is moderate on scattered myofibers. C, D: Muscle biopsy of a 25-year-old African woman harboring anti-U1snRNP and anti-Ro autoantibodies. She suffered from “mixed connective tissue disease” with myositis, systemic lupus erythematosus, rheumatoid arthritis, interstitial lung disease, pericarditis, Raynaud phenomenon, and puffy fingers. Hematoxylin-stained frozen section (C) shows variations in myofiber sizes and moderate endomysial lymphocytic infiltrates. MHC class I immunostaining (D) highlights several scattered myofibers.

Figure 2.. A, B, C: Muscle biopsy of a 47-year-old Caucasian woman harboring anti-Jo1 autoantibodies and suffering from an anti-synthetase syndrome with myositis, interstitial lung disease, and arthritis. Hematoxylin-stained frozen section (A) shows variations in myofiber sizes and necrotic fibers in the perifascicular area. MHC class I immunostaining (B) highlights the perifascicular lesions, and sarcolemmal C5-b9 complement deposition (C) is observed on the perifascicular area (arrows). D, E, F: Muscle biopsy of a 43-year-old Caucasian man harboring HMGCR autoantibodies and suffering from severe rhabdomyolysis but no extramuscular manifestation. Hematoxylin-stained frozen section (D) shows scattered necrotic myofibers with myophagocytosis (arrows), in the absence of significant lymphocytic infiltration. MHC class I immunostaining (E) is diffuse with focal enhancement around areas of myophagocytosis. The C5-b9 complement deposition (F) is patchy on the sarcolemma of some non-necrotic myofibers (arrows). G, H, I: Muscle biopsy of a 43-year-old Caucasian man harboring anti-Mi-2 autoantibodies and suffering from dermatomyositis with the characteristic skin rash. Hematoxylin-stained frozen section (G) shows perifascicular atrophy with necrosis and regeneration of myofibers, and lympho-macrophagic infiltrates. MHC class I immunostaining (H) highlights the perifascicular lesions, and the C5-b9 complement deposition (I) is observed on the capillaries (arrows). J, K, L: Muscle biopsy of a patient harboring anti-TIF1-γ and anti-Ro autoantibodies. This 80-year-old Caucasian man suffering from prostate and lung cancers presented an overlap syndrome associating dermatomyositis with edematous systemic sclerosis. Hematoxylin-eosin (J) and Gomori trichrome (K) frozen sections show an extensive necrosis of myofibers, non-rimmed vacuoles (arrows), and interstitial edema. Inflammatory cell infiltrates are not obvious. MHC class I immunopositivity of myofibers is extensive (L), and C5-b9 complement deposition on capillaries is masked by the strong and diffuse unspecific immunostaining of myofibers under necrosis (not shown). Bars = 100 µm.