Inflammatory myopathy with abundant macrophages (IMAM): A condition sharing similarities with cytophagic histiocytic panniculitis and distinct from macrophagic myofasciitis

Guillaume Bassez, Francois Jérôme Authier, Emmanuèle Lechapt-Zalcman, Marie Hélène Delfau-Larue, Anne Plonquet, Michelle Coquet, Isabel Illa, Romain K. Gherardi

Research output: Contribution to journalReview articleResearchpeer-review

40 Citations (Scopus)

Abstract

We describe the unreported pattern of inflammatory myopathy with abundant macrophages (IMAM) as a main differential diagnosis of postimmunization aluminum hydroxide-induced macrophagic myofasciitis (MMF). IMAM was mainly detected among patients with a dermatomyositis (DM)-like disease. Among 113 muscle biopsies from DM patients collected from 1974 to 2000, intensity of macrophage infiltration was highly variable: 41.5% (-/+); 34.5% (+); 17% (++); and 7% (+++). The 27 patients from groups (++) and (+++) had a similar pattern of macrophagic infiltration and were considered to have IMAM. They were compared to 40 MMF patients. In IMAM, macrophage infiltrates were diffuse and correlated positively with both T cell infiltrates and acute muscle fiber damage, and showed pictures of hemophagocytosis (21/27). Connective tissue structures were infiltrated by noncohesive, ribbon-forming collections of large basophilic macrophages containing no crystalline inclusions. In MMF, macrophage infiltrates were focal and formed compact well-delineated aggregates of granular PAS+ cells, loaded with crystalline aluminum hydroxide particles, in the absence of either hemophagocytosis or conspicuous muscle damage. Review of the literature indicates similarities between IMAM and "cytophagic histiocytic panniculitis" (CHP), a condition characterized by T cell-triggered macrophage hyperactivation. Both IMAM and CHP, but not MMF, may be associated with a life-threatening hemophagocytic syndrome.
Original languageEnglish
Pages (from-to)464-474
JournalJournal of Neuropathology and Experimental Neurology
Volume62
Issue number5
DOIs
Publication statusPublished - 1 May 2003

Keywords

  • Dermatomyositis
  • Fasciitis
  • Hemophagocytic syndrome
  • Histiocytosis non-Langerhans cell
  • Macrophage
  • Myositis
  • Panniculitis

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