Macrophagic myofasciitis and aluminium-containing
The emergence of a new type of histopathological lesion of unknown origin called macrophagic myofasciitis (MMF), characterized by a unique myopathological pattern, has been reported by the Groupe d’études et recherche sur les maladies musculaires acquises et dysimmunitaires (GERMMAD) of the Association française contre les myopathies.
MMF is characterized by centripetal infiltration of the pimysium, perimysium and perifascicular endomysium by non-periodic-acid-shiff (PAS) positive cells of macrophage lineage with osmiophilic crystal inclusions. MMF has been mainly detected by deltoid muscle biopsy in adult patients, although it has also been detected by quadriceps muscle biopsy in 3 young children. The histopathological lesion is localized at these sites. There is absence of necrosis (of both epithelioid and giant cells) and of mitotic figures, and inconspicuous muscle fibre damage. Determination of the chemical nature of the macrophage inclusions by nuclear microprobe, X-ray microanalysis and atomic absorption spectrometry showed that they were composed of aluminium salts. Since aluminium salts are used as an adjuvant in a number of vaccines administered intramuscularly into deltoid and quadriceps muscles, it has been hypothesized that MMF may represent an unusual reaction to intramuscular injections of aluminium-containing vaccines. Since muscle biopsies are only carried out in patients with myopathic symptoms, there is at present no information on whether the characteristic local histological pattern can occur in the normal healthy population after vaccination.
To determine whether a causal relationship can be established between MMF and aluminium-containing vaccines, the Vaccine Safety Advisory Committee was convened together with GERMADD scientists, acknowledged experts in the field of neuromuscular diseases and aluminium adjuvants, and representatives from industry, the French Ministry of Health, the Agence française de sécurité sanitaire des produits de santé and the Institut de veille sanitaire.