Juvenile polymyositis or paediatric muscular dystrophy: a detailed re‐analysis of 13 cases

Abstract

Inflammatory changes in apparently sporadic juvenile myopathies should prompt consideration of an early presentation of MD. Detailed analysis of muscle histopathology, specifically the detection of subsarcolemmal blebbing, isolated fibre degeneration occurring independent of inflammatory infiltrates, patchy clustered major histocompatibility complex-I expression and a CD68+/CD3+ perimysial infiltrate, assists in the diagnosis of early MD. Specific protein and gene analysis adds support to the pathological diagnosis of dystrophy. This series adds weight to suggestions that JPM may not represent a discrete clinical or pathological entity.

Myositis or dystrophy? Traps and pitfalls

“…The existence of polymyositis in childhood is greatly debated (whereas dermatomyositis is well-recognised). The presence of inflammatory infiltrates within muscle of young people (without skin features of dermatomyositis) is more likely to be seen as a feature of paediatric LGMD or Duchenne/Becker muscular dystrophy than primary myositis [22]. Moreover, LMNA mutations were recently reported in patients showing substantial inflammatory infiltrates in the muscle biopsy, which could lead to diagnostic error [23].…”

Dysferlinopathy misdiagnosed with juvenile polymyositis in the pre-symptomatic stage of hyperCKemia: a case report and literature review

“…Over time, PM has been questioned as a distinct entity, and many of these patients may be better described as having an alternative diagnosis [ 11 – 15 ]. Dermatomyositis is well recognized in children, but the existence of juvenile PM has been highly debated [ 16 , 17 ]. In fact, it took almost 10 years to recruit enough patients to establish the current EULAR/ACR criteria for adult and juvenile IIM, and even then, the number of children with PM was insufficient for adequate study.…”

“…Therefore, the differential diagnosis of PM from muscular dystrophies, based upon histologic and clinical findings, may be challenging [ 18 , 19 ]. In a retrospective clinicopathological analysis from Australia, for example, of 13 cases with an initial diagnosis of juvenile PM, 12 (92.3%) were found to be muscular dystrophy, suggesting that juvenile PM is extremely uncommon, if it exists at all [ 17 ].…”

Clinical and Laboratory Features Distinguishing Juvenile Polymyositis and Muscular Dystrophy

“…The differences in the biopsy features that we observed included the myopathic features, which were more frequent in the dystrophy group, including myofiber size variation, fiber hypertrophy, and hypercontracted fibers. In a previous study in which 13 patients were misdiagnosed with juvenile PM and had undetected dystrophies, the distinguishing biopsy features in patients with dystrophies included subsarcolemmal blebbing, isolated fiber degeneration without accompanying inflammation, and a perimysial infiltrate consisting of macrophages (). We did not find differences in these latter biopsy features in this study and did not examine subsarcolemmal blebbing.…”

“…Some forms of muscular dystrophies in children can mimic juvenile PM. However, juvenile PM and dystrophies have different biopsy characteristics, including immunopathologic features, but share some common clinical manifestations (). The histopathologic hallmark of juvenile PM is the presence of endomysial lymphocytic infiltration, but muscle inflammation has been reported in some dystrophies, including Duchenne's muscular dystrophy, facioscapulohumeral muscular dystrophy, limb‐girdle muscular dystrophy type 2B, and congenital muscular dystrophy with primary merosin deficiency ().…”