Systemic histiocytosis presenting as macrophagic myofasciitis.

A patient with the distinctive pathologic findings of macrophagic myofasciitis (MMF) is presented. This case is similar to patients with MMF first seen in France in 1993. The French group ruled out a histiocytic disorder, and later (1999) reported that this disorder represented an unusual focal reaction to intramuscular injections of vaccines containing aluminum. More recently (2001) symptomatic demyelinating disease was reported in 8 of the 92 patients with MMF who were recognized in France. The present case has thickening of the aortic and mitral valves, a finding not reported by the French group. Whereas the French group ruled out a histiocytic etiology for MMF in their patients, the cardiac findings, along with the innumerable small patchy abnormalities in the supratentorial white matter identified on magnetic resonance imaging (MRI), likely implicate a systemic histiocytic basis for this patient's unique disorder. The importance of an exhaustive workup of the patient with multiple sclerosis with diffuse myalgias is reemphasized.