Human actinomycosis is a rare, chronic, suppurative, and granulomatous bacterial infection first described by Israel in 1878.1,2 Actinomycosis is characterized by abscesses, tissue fibrosis, and draining sinuses that may discharge sulfur granules.2-4 Actinomyces species are gram-positive anaerobic filamentous commensal organisms.1,2,5-7 Six species of Actinomyces are responsible for human disease; however, most cases of human actinomycosis are due to Actinomyces israelii.2 The 5 major clinical manifestations of actinomycosis in order of frequency are cervicofacial, thoracic, abdominal, pelvic, and cutaneous.1-3,5,7 Primary cutaneous actinomycosis is an exceedingly rare infection in children and is usually related to external trauma. We present the case of a 9-year-old boy who developed primary cutaneous actinomycosis of the scalp 5 years after cranial trauma related to a motor vehicle accident.
A 9-year-old Hispanic boy was referred to the pediatric infectious disease (ID) clinic by his primary care physician for a large fungating mass overlying the left temporoparietal scalp believed to represent a staphylococcal infection (Fig. 1A). His medical history was significant for a history of a left temporoparietal skull fracture with associated encephalomalacia resulting from a motor vehicle accident that occurred when he was 2 years old. The scalp mass first appeared approximately 5 years after that trauma. The mass had been surgically excised twice by a local plastic surgeon within the initial months after its appearance. Surgical specimens were sent for culture and pathological evaluation. After the second resection, the patient was lost to follow-up. The mass returned and progressively enlarged. The patient subsequently received his medical care from various emergency departments and urgent care centers. He received numerous short courses of various combinations of topical and oral steroids and antibiotics without an established diagnosis or further diagnostic attempts. He occasionally noted transient improvement of the scalp mass with some of the therapeutic interventions; however, the mass persisted.
Upon initial evaluation in the pediatric ID clinic, the patient was noted to have a large fungating nontender mass overlying the left temporoparietal scalp with multiple sinuses draining purulent material (Fig. 1A). The patient was admitted to the hospital to facilitate a diagnostic evaluation and to institute therapy. He had an extensive immunologic evaluation with normal results. Computed tomography scan of the head demonstrated stable encephalomalacia and no evidence of intracranial extension of the infection. Previous pathology specimens were located, and the slides were reviewed. The original pathology slides demonstrated colonies of gram-positive filamentous bacteria (sulfur granule) surrounded by areas of acute and chronic inflammation consistent with actinomycosis (Figs. 1B, C) and birefringent foreign material (Fig. 1D). Grocott-Gomori methenamine-silver and acid-fast bacilli stains showed no fungal organisms or acid-fast bacilli. No organism was isolated on culture. Repeat biopsy was carried out to assess for malignant transformation and to attempt to culture the infectious etiology. Repeat biopsy specimens did not demonstrate malignancy or grow Actinomyces. The patient was placed on high-dose intravenous ampicillin/sulbactam for primary cutaneous actinomycosis based on the characteristic pathology findings. After completing 6 weeks of intravenous antibiotics, the patient was changed to high-dose oral amoxicillin.
Approximately 3 months after initiating antimicrobial therapy, the patient was taken to the operating theater where a wide local excision of the 15 × 11-cm scalp mass was performed by the university-affiliated plastic surgeon (R.K.K.). The mass was excised in its entirety. After the excision, a wound vacuum-assisted closure device was used for 6 weeks to cover the wound and to promote healthy granulation response. Six weeks after excision of the scalp mass, no abnormal granulation tissue or recurrence of the mass was noted, and the patient underwent a split thickness skin grafting without complications.
The patient has been followed in the pediatric ID clinic regularly. He has completed a 12-month course of antibiotics without recurrence of the scalp mass and without adverse drug-related events. The combination of antimicrobial therapy and plastic surgery intervention treated the infection and resulted in an acceptable cosmetic appearance.
Human actinomycosis is usually attributable to A. israelii 1-4,8-10; however, Actinomyces naeslundi,1,2,8 Actinomyces odontolyticus,1,2 Actinomyces viscosus,1,2,8 Actinomyces meyeri,1,2 and Actinomyces gerencseriae, 2 have also been reported in the literature. Actinomyces species are gram-positive anaerobic filamentous bacteria1,2,5-7 existing as commensals within the human oral cavity, gastrointestinal tract, and female genital tract.1,2,5,9 Actinomycosis is an endogenous disease. No pathogenic species of Actinomyces has ever been isolated from environmental sources,2,5,8 and no person-to-person transmission has ever been documented.2,5 Actinomyces species are of low pathogenicity and are unable to penetrate healthy tissue.1,5 Actinomycosis occurs much more commonly in adults1,9 and is 3 to 4 times more prevalent in men.1,3,7
The 5 major clinical manifestations of actinomycosis in order of frequency are cervicofacial, thoracic, abdominal, pelvic, and primary cutaneous.1-3,5,7 Cervicofacial actinomycosis exhibits a predilection for the mandible1,5 and is often associated with antecedent dental procedures and odontogenic infections.2,4,9 Thoracic actinomycosis usually results from aspiration of oropharyngeal secretions and presents as a chronic pneumonia.2 Abdominal actinomycosis may be a complication of intestinal perforation, penetrating trauma, or manipulation of the gastrointestinal tract and may involve any of the intestinal viscera, frequently presenting with an insidious course.2 Pelvic actinomycosis may be the result of the direct extension of abdominal actinomycosis into the pelvis, or it may be associated with infection of intrauterine contraceptive devices.2 Cutaneous actinomycosis is usually the result of the extension of underlying disease.3 Primary cutaneous actinomycosis is a very uncommon form of actinomycosis because of the endogenous habitat of pathogenic Actinomyces species.3,5,6 Primary cutaneous actinomycosis has an association with preceding trauma,3,5,6,8,10 tissue ischemia,5 and oral-cutaneous contact.5,6
Actinomycosis should be considered in the differential diagnosis for any patient presenting with a subacute or chronic inflammatory lesion. Clinical features that should increase the suspicion of actinomycosis include the presence of multiple draining sinuses that may spontaneously close and reopen,4,5,8 transient improvement in lesions with short courses of empirical antibiotics,9 and the presence of sulfur granules discharged from the draining sinuses.3,4,7-9 Histopathologic evaluation reveals a neutrophil inflammatory infiltrate surrounding central sulfur granules that appear as round, oval, or lobulated basophilic granules.4,9 Closer examination of the sulfur granules reveals radiating gram-positive, beaded, and filamentous organisms that are negative on Ziehl-Neelsen acid-fast staining.5-7 The typical appearance and staining characteristics of the sulfur granules help to differentiate actinomycosis from nocardiosis and botryomycosis. Histopathologic evaluation of suspected actinomycosis may be difficult because up to 25% of lesions may contain only 1 sulfur granule.2 Isolation of an Actinomyces organism in culture from a clinical specimen remains the definitive diagnostic technique; however, cultures may be positive in only 25% to 50% of cases5-7,10 and may require extended periods of incubation.2
High-dose intravenous penicillin for 4 to 6 weeks followed by high-dose oral penicillin or amoxicillin for 6 to 12 months remains the therapeutic regimen of choice for all forms of actinomycosis.1-3,9 For patients unable to take penicillin, alternative antibiotics include clindamycin, erythromycin, tetracyclines, and chloramphenicol.1-4,9 Surgical resection of masses or drainage of abscesses may serve as useful adjunctive therapies, especially with large masses, but surgery alone is not curative.2,4,5
Our case is significant for several reasons. First, primary cutaneous actinomycosis is an exceedingly rare infection in children. Second, our patient's clinical course in the 2 years before his being evaluated in the pediatric ID clinic is characteristic for actinomycosis, including the presence of multiple draining sinuses that spontaneously closed and reopened, transient improvement in lesions with short courses of empirical oral antibiotics, and the history of antecedent trauma. Third, our patient has responded very well to a combination of antibiotics and surgical intervention. Finally, this case also demonstrates the need to maintain a high index of suspicion for primary cutaneous actinomycosis in pediatric patients. Although often difficult and delayed, accurate diagnosis of primary cutaneous actinomycosis is essential for proper treatment of this uncommon infection.
The authors thank Dr Andrew C. Hoot for providing the photomicrographs.
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