African-American woman presents to her primary care
physician's office with a history of right-sided chest
discomfort and intermittent dry cough of 4 weeks' duration.
She denies having a fever, chest pressure, night sweats,
hemoptysis, or weight loss. However, she does admit to a
25–pack-year history of smoking and denies using any
illicit drugs. She has not recently traveled outside the
On physical examination, she is afebrile with a normal
heart rate and blood pressure. She is a well-developed,
thin woman who appears to be in no apparent distress.
Findings from the patient's lung and heart examination are
unremarkable. Findings from the remainder of the
examination are also unremarkable.
The chest radiograph (see Image 1) demonstrates a cavitary
mass in the right upper lobe of the lung. Follow-up chest
CT (see Image 2) shows the same cavitary mass as a
thick-walled lesion in the posterior segment of the right
upper lobe. It measures 4.2 X 5.5 cm.
The patient is initially given a 2-week course of oral
clindamycin. However, follow-up chest images obtained
approximately 1 month afterward fail to reveal any interval
improvement. A positron emission tomographic (PET) scan is
subsequently obtained and shows abnormal
[18F]-fluorodeoxyglucose (FDG) uptake in the right
posterior and apical segments of the right upper lobe and
right hilar lymph node with no other foci of abnormal
uptake. Ultrasonography-guided aspiration and core
lung-mass biopsy are performed, but the results are
The patient eventually undergoes thoracotomy and right
upper lobectomy. Biopsy specimens are obtained. The
pathology specimen shows evidence of acute necrotizing
bronchopneumonia and a cavitary abscess. Silver staining
demonstrates aggregates of filamentous organisms (see Image
What is the organism, and what is the diagnosis?
actinomycosis: Before the pathology specimen was
obtained, tuberculin skin testing, sputum analysis
for acid-fast bacilli, and routine cultures were
also ordered; all findings were negative. Additional
laboratory studies, including a serum creatinine
determination, yield normal levels. HIV serology
also returned a negative result. The stain shown in
Image 3 demonstrates aggregates of filamentous
organisms highlighted with silver stain. This
pattern is consistent with actinomyces, and
pulmonary actinomycosis is diagnosed.
The differential diagnosis of a cavitary lung mass
consists of a wide variety of pulmonary diseases.
Some, such as bronchogenic carcinoma, tuberculosis
(TB), and suppurative lung disease, are common, and
others, such as actinomycosis, are relatively
On clinical evaluation, pulmonary actinomycosis is
commonly confused with TB, suppurative lung disease,
and malignancy. Patients with pulmonary
actinomycosis usually present with a pulmonary
consolidation. However, as in this case, some
patients present with cavitation and spread to the
adjacent tissues. Bronchoscopic findings are usually
nondiagnostic, and most patients require open lung
biopsy. The organism involved in this condition is Actinomyces
israelii. This microorganism is slender,
branching gram-positive bacillus embedded in the
matrix of the sulfur granules. The hallmark of
actinomycosis is the formation of the yellow sulfur
The optimal duration of treatment is not clearly
established, and the traditional recommendation of
intravenous antibiotic therapy (beta-lactam) for 2-6
weeks followed by oral antibiotic therapy for 6-12
months is not always necessary. The condition is
best treated with individualized therapeutic
protocols depending on factors such as the initial
burden of disease, the patient's response to and the
success of surgical resection, and the patient's
progressive clinical and radiologic response to
continuing antibiotic regimens. The most common
indications for surgery are hemoptysis and empyema.
As a complication, chronic sinus drainage has become
decreasingly frequent, presumably because of the
widespread use of the antibiotics.
The patient in this case responded well to
antibiotic therapy continued postoperatively. She
completed a 6-month course of amoxicillin with no
clinically significant adverse effects. During
follow-up, a repeat chest CT scan showed no evidence
of active disease.
to further Information on:
more information on pulmonary actinomycosis, see the
eMedicine articles Actinomycosis
(within the Pediatrics specialty), Actinomycosis
(within the Internal Medicine specialty), and Pulmonary
Angiography (within the Radiology specialty).