Microbiology · Year 2 · from Microbiology
Case 2: Actinomycosis
Presentation
A 55-year-old woman with a history of dental neglect presents with a 2-month history of a slowly enlarging mass on her right jaw that has recently developed a draining sinus tract. She reports mild pain, low-grade fevers, and weight loss. Examination reveals a firm, non-tender mass involving the right mandible with purulent drainage from a sinus tract. The drainage contains small yellowish granules. CT scan shows a soft tissue mass with bony erosion that crosses fascial planes.
Clinical Image
Yellow-white sulfur granules visible in purulent drainage from a sinus tract - the pathognomonic finding in actinomycosis.
Image Source: Lecture image - Actinomyces infections
Questions
- What is the diagnosis, and what organism is responsible?
- What are the characteristic clinical features that distinguish this infection from malignancy?
- Why does this infection have a propensity to form draining sinuses and cross tissue planes?
- What is the recommended treatment approach?
Answers
- Diagnosis and organism: The diagnosis is cervicofacial actinomycosis, also known as "lumpy jaw," caused by Actinomyces israelii or related species. Despite the name ending in "-myces," Actinomyces are true bacteria, not fungi. They are anaerobic to microaerophilic gram-positive rods that demonstrate characteristic branching filamentous morphology. The yellowish granules (sulfur granules) are aggregates of Actinomyces organisms.
- Distinguishing features from malignancy: Several features help distinguish actinomycosis from malignancy: the presence of draining sinus tracts (uncommon in malignancy), identification of sulfur granules (pathognomonic), the tendency to cross tissue planes without respect for anatomic boundaries (unusual for most infections but shared with some aggressive malignancies), and indolent progression over weeks to months. However, given the overlap in presentation, biopsy and culture are essential.
- Propensity for sinus tracts and tissue plane invasion: Actinomyces produces proteolytic enzymes that facilitate tissue destruction and spread. Unlike most infections that are contained by fascial planes, actinomycosis characteristically crosses anatomic boundaries, spreading from one compartment to another. This creates the appearance of a infiltrative mass that can mimic malignancy. Draining sinuses form when chronic infection erodes through soft tissues to the skin surface, creating persistent fistulous tracts.
- Treatment approach: Treatment requires prolonged high-dose antibiotic therapy due to the slow growth of the organism and its ability to sequester within fibrotic tissue. Penicillin G (or amoxicillin) is the drug of choice, typically administered for 6-12 months (often 2-6 weeks IV followed by oral therapy). Doxycycline is an alternative for penicillin-allergic patients. Surgical intervention may be needed to debride bulky disease, remove necrotic tissue, or drain abscesses. In IUD-associated pelvic actinomycosis, device removal is essential.