Macrophagic Myofasciitis, or MMF, is a rare muscle disease identified in 1993. The disease is characterized by microscopic lesions found in muscle biopsies that show infiltration of muscle tissue by PAS-positive macrophages.[1] Specific causes of MMF are unknown, but the disease is most often associated with the pathological persistence of aluminium hydroxide used in some vaccines. Clinical symptoms include muscle pain, joint pain, muscle weakness, fatigue, fever, and muscle tenderness. A diagnosis can only be identified with an open muscle biopsy of the vaccinated muscle.[2]