Journal Article

Inflammatory Myopathy with Abundant Macrophages (IMAM): A Condition Sharing Similarities with Cytophagic Histiocytic Panniculitis and Distinct from Macrophagic Myofasciitis

COQUET, MICHELLE, ILLA, ISABEL, LECHAPT-ZALCMAN, EMMANUÈLE, DELFAU-LARUE, MARIE HÉLÈNE, PLONQUET, ANNE, BASSEZ, GUILLAUME, AUTHIER, FRANCOIS-JÉRÔME, GHERARDI, ROMAIN K.

2003

Overview

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 variable41.5% (−/+); 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.

• Publisher: American Association of Neuropathologists, Inc,Lippincott Williams & Wilkins,Oxford University Press
• Subject: Adolescent / Adult / Aged / Aged, 80 and over / Biological and medical sciences / Child / Child, Preschool / Diagnosis, Differential / Diseases of striated muscles. Neuromuscular diseases / Fasciitis - pathology / Female / France / Histiocytes / Humans / Lymphocytes / Macrophages / Male / Medical sciences / Microscopy, Electron / Middle Aged / Muscle Fibers, Skeletal - pathology / Muscle, Skeletal - pathology / Myositis - pathology / Necrosis / Neurology / Panniculitis - pathology / Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis