Actinomycosis

• Caused by actinomyces israeli, a gram+ pleomorphic anaerobic bacterium related to the morphology of a fungus and Mycobacterium—not acid fast

• At one time, it was the most common pulmonary fungal disease

• White or yellow “sulfur granules” in exudate are really mycelial clumps

• Rod shaped form is found “normally” in dental caries, gingival margins, tonsillar crypts and GI tract

• People with very poor dental hygiene and those that are immunosuppressed are predisposed

• Affects mandibulofacial area, intestinal tract and lung, in that order

Mandibulofacial

• Osteomyelitis of the mandible — with soft tissue mass – “lumpy jaw”

Intestinal

• Resembles Crohn’s disease

• May produce rupture of a hollow viscous, especially appendix

• May produce fistula formation

Pulmonary 

• Consolidation which extends across fissure — peripheral and lower lobe

  • DDX for lung consolidation which extends through chest wall:

    • Blastomycosis

    • TB

    • Crytococcosis

• Abscess

• Empyema

• Osteomyelitis of the rib — wavy periosteal reaction, rarely rib destruction

• Draining chest wall sinuses

• If chronic, it results in severe fibrosis