[show abstract][hide abstract] ABSTRACT: Macrophagic myofasciitis has been almost exclusively detected in adults only. We describe six children of Arab Moslem origin with this disorder. Three presented with hypotonia, developmental delay and seizures and were evaluated for a mitochondrial disorder. The other three children had hypotonia and predominantly motor delay. Five of the six families were consanguineous. A massive collection of macrophages was present in the fascia and adjacent epimysium in all biopsies. The macrophages were periodic-acid-Schiff positive and immunoreactive for CD68. One biopsy which was evaluated by electron microscopy and energy-dispersive X-ray microanalysis showed crystalline structures containing aluminum in macrophages. Two children with motor delay and hypotonia were treated with oral prednisone for 3 months with no clinical improvement. Genetic predisposition probably accounts for the variability in the prevalence of macrophagic myofasciitis in different populations. At least in childhood, there seems to be no connection between macrophagic myofasciitis as a pathological entity and the clinical symptoms and signs.