Skin nontumor

Infectious disorders

Actinomycosis


Editorial Board Member: Kiran Motaparthi, M.D.
Abha Soni, D.O., M.P.H.

Last author update: 24 June 2022
Last staff update: 24 January 2023

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PubMed Search: Actinomycosis skin

Abha Soni, D.O., M.P.H.
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Cite this page: Soni A. Actinomycosis. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skinnontumoractinomycosis.html. Accessed June 16th, 2024.
Definition / general
Essential features
  • Causative agent Actinomyces israelli
  • Treated with high dose penicillin
  • Splendore-Hoeppli phenomenon is a histologic feature
Terminology
  • Most common causative agent is Actinomyces israelii
  • Sulfur granules: small yellow granules found within the abscesses formed by Actinomyces infection (Ophthal Plast Reconstr Surg 1992;8:237)
  • Lumpy jaw syndrome: large abscesses located on the head and neck, usually following dental disease and mandibular osteomyelitis (BMJ Case Rep 2015;2015:bcr2014206557 )
  • Splendore-Hoeppli phenomenon (asteroid bodies): pink rim at the periphery of the colony, due to immunoglobulin and cell debris, which occurs around colonies of fungi, bacteria and parasites (J Oral Maxillofac Pathol 2018;22:161)
ICD coding
  • ICD-10: A42.9 - actinomycosis, unspecified
Epidemiology
Sites
  • Cervicofacial (post dental infection), skin (posttraumatic injury creating an anaerobic environment), pelvic (post intrauterine device placement), abdominal (status post ruptured appendix or bowel perforation) and pulmonary (smokers with poor dental hygiene, aspiration of infective material) (Infect Drug Resist 2014;7:183)
Pathophysiology
  • Predisposing factors include poor oral hygiene, trauma, male gender, diabetes mellitus, immunosuppression, alcoholism and malnutrition (Infect Drug Resist 2014;7:183)
  • Filamentous bacteria are a normal commensal inhabitant of the oral and buccal cavities, gastrointestinal tract and female genitalia
  • Etiology of infection in skin is commonly linked with a traumatic injury, human bite or a perforating injury, which creates an anaerobic environment for Actinomyces israelii to grow in (J Clin Diagn Res 2014;8:YD03)
Etiology
  • Caused by Actinomyces israelii in humans and Actinomyces bovis in animals
Clinical features
  • Localized pain, swelling and draining fistulas
Diagnosis
  • Culture on chocolate agar media at 37 °C
  • Gram stain is more sensitive than culture, especially if patient is on antibiotics
  • Filamentous bacteria of actinomycosis can be identified on H&E and are highlighted by Gram stain (Infect Drug Resist 2014;7:183)
  • Polymerase chain reaction (PCR) and nucleic acid probes are being developed for faster and more accurate identification
Case reports
Treatment
  • High dose penicillin is necessary to penetrate areas of fibrosis and suppuration / granules (Clin Infect Dis 2004;38:444)
  • Drainage of abscesses or radical excision of sinus tracts
Clinical images

Contributed by Dhiraj B. Nikumbh, M.B.B.S., M.D.
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Multiple sinuses in foot



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Indurated lesion

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Lesion over back

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Left thigh lesion

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Molar tooth appearance

Gross description
  • Firm, swollen region on the skin with multiple draining abscesses and fistula tracts
  • Pus draining yellow sulphur granules
Gross images

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Outer / inner surface and cross section of excised tissue

Microscopic (histologic) description
  • Lymphocytes, neutrophils, giant cells and fibroblasts
  • Bacterial colonies (sulphur granules) found at the center of the inflammatory reaction, composed of basophilic radiating filaments
Microscopic (histologic) images

Contributed by Kuroli Eniko, M.D., Yale Rosen, M.D. and Haitham Alfalah, M.D. (source: Wikipedia)
Suppurative and granulomatous inflammation

Suppurative and granulomatous inflammation

Dense sheets of neutrophils

Dense sheets of neutrophils

Colony of Actinomyces Colony of Actinomyces

Colony of Actinomyces


Thin gram positive filamentous organisms Thin gram positive filamentous organisms Thin gram positive filamentous organisms

Thin gram positive filamentous organisms

Grocott stain

Grocott stain

Gram stain

Gram stain

Cytology description
  • Mixed inflammatory infiltrate, foreign body multinucleated giant cells and clumps of filamentous organisms
Cytology images

Contributed by Dhiraj B. Nikumbh, M.B.B.S., M.D.
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Mixed inflammatory infiltrate with clumps of fibrillar organisms



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Gram stain

Positive stains
Negative stains
Sample pathology report
  • Skin, biopsy:
    • Primary cutaneous actinomycosis
Differential diagnosis
  • Nocardiosis:
    • Branching filamentous bacteria are partially acid fast positive
    • Histologic appearance of Nocardia is similar to other actinomycetes family members; culture and biochemical testing is necessary for diagnosis / identification
    • Fite-Faraco stain is helpful since positive in nocardiosis
  • Tuberculosis:
    • Characteristic histologic findings include caseating granulomas
    • Detected by Ziehl-Neelsen stain and Mycobacterium culture
  • Sporotrichosis:
    • Characteristic histologic findings include mixed acute and chronic inflammatory response
    • Organisms "sporothrix asteroids" can be detected via PAS, GMS stains
  • Paracoccidioidomycosis:
    • Characteristic histologic findings include mixed acute and chronic inflammatory response
    • Organisms referred to as captain wheel on morphology can be detected via PAS, GMS stains
Board review style question #1

What is the name of the unique histologic pattern that takes place in a cutaneous actinomycosis infections?

  1. Asteroid body reaction
  2. Flame figures
  3. Gout
  4. Splendore-Hoeppli phenomenon
Board review style answer #1
D. Splendore-Hoeppli phenomenon

Comment Here

Reference: Actinomycosis
Board review style question #2
What type of ​granules are found within the abscesses formed by Actinomyces infection?

  1. Metachromatic granules
  2. Polyphosphate granules
  3. Polysaccharide granules
  4. Sulfur granules
Board review style answer #2
D. Sulfur granules

Comment Here

Reference: Actinomycosis
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