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The clinical presentations of actinomycosis are myriad. Common in the preantibiotic era, actinomycosis has diminished in incidence, as has its timely recognition. Actinomycosis has been called the most misdiagnosed disease, and it has been said that no disease is so often missed by experienced clinicians. Thus this entity remains a diagnostic challenge. Etiologic Agents
Actinomycosis is most commonly caused by A. israelii. A. naeslundii, A. odontolyticus, A. viscosus, A. meyeri, A. gerencseriae, and Propionibacterium propionicum are established but less common causes. Most if not all actinomycotic infections are polymicrobial. Actinobacillus actinomycetemcomitans, Eikenella corrodens, Enterobacteriaceae, and species of Fusobacterium, Bacteroides, Capnocytophaga, Staphylococcus, and Streptococcus are commonly isolated with actinomycetes in various combinations, depending on the site of infection. Epidemiology
Actinomycosis has no geographic boundaries and occurs throughout life, with a peak incidence in the middle decades.
Males have a threefold higher incidence than females, possibly because of poorer dental hygiene and/or more frequent trauma.
Factors that have probably contributed to the decrease in actinomycosis incidence since the advent of antibiotics include improved dental hygiene and the initiation of antimicrobial treatment before the disease develops fully. Pathogenesis and Pathology
The etiologic agents of actinomycosis are members of the normal oral flora and are often cultured from the bronchi, the gastrointestinal tract, and the female genital tract.
The critical step in the development of actinomycosis is disruption of the mucosal barrier. Local infection may ensue. Once established, actinomycosis spreads contiguously in a slow progressive manner, ignoring tissue planes. Although acute inflammation may initially develop at the infection site, the hallmark of actinomycosis is the characteristic chronic, indolent phase manifested by lesions that usually appear as single or multiple indurations. Central necrosis consisting of neutrophils and sulfur granules develops and is virtually diagnostic. Clinical Manifestations
Oral-Cervicofacial Disease
Actinomycosis occurs most frequently at an oral, cervical, or facial site, usually as a soft tissue swelling, abscess, or mass lesion that is often mistaken for a neoplasm. The angle of the jaw is generally involved, but a diagnosis of actinomycosis should be considered with any mass lesion or relapsing infection in the head and neck . Otitis, sinusitis, and canaliculitis also can develop. Pain, fever, and leukocytosis are variably reported. Contiguous extension to the cranium, cervical spine, or thorax is a potential sequela. Thoracic Disease
Thoracic actinomycosis usually follows an indolent progressive course, with involvement of the pulmonary parenchyma and/or the pleural space. Chest pain, fever, and weight loss are common. A cough, when present, is variably productive. Mediastinal infection is uncommon, usually arising from thoracic extension but rarely resulting from perforation of the esophagus, from trauma, or from head and neck or abdominal disease. Abdominal Disease
Abdominal actinomycosis poses a great diagnostic challenge. Months or years usually pass from the inciting event appendicitis, diverticulitis, peptic ulcer disease, foreign-body perforation, bowel surgery, or ascension from IUCD-associated pelvic disease to clinical recognition. Because of the flow of peritoneal fluid and/or the direct extension of primary disease, virtually any abdominal organ, region, or space can be involved.
The disease usually presents as an abscess, a mass, or a mixed lesion that is often fixed to underlying tissue and mistaken for a tumor. Pelvic Disease
Actinomycotic involvement of the pelvis occurs most commonly in association with an IUCD. When an IUCD is in place or has recently been removed, pelvic symptoms should prompt consideration of actinomycosis. The risk, although not quantified, appears small. The disease rarely develops when the IUCD has been in place for less than 1 year, but the risk increases with time.
Actinomycosis can also present months after IUCD removal. Symptoms are typically indolent; fever, weight loss, abdominal pain, and abnormal vaginal bleeding or discharge are the most common. The earliest stage of disease is often endometritis and commonly progresses to pelvic masses or a tubo ovarian abscess .Unfortunately, because the diagnosis is often delayed, a "frozen pelvis" mimicking malignancy or endometriosis. Central Nervous System Disease
Actinomycosis of the central nervous system (CNS) is rare. Single or multiple brain abscesses are most common.
Musculoskeletal and Soft Tissue Infection
Actinomycotic infection of bone is usually due to adjacent soft-tissue infection but may be associated with trauma such as fracture of the mandible or hematogenous spread. Investigations:
Aspirations and biopsies (with or without CT or ultrasound guidance) are being used successfully to obtain clinical material for diagnosis, although surgery may be required. The diagnosis is most commonly made by microscopic identification of sulfur granules an in vivo matrix of bacteria, calcium phosphate, and host material in pus or tissues.
CT and magnetic resonance imaging (MRI) are generally the most sensitive
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