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Primary cutaneous actinomycosis on the chest wall

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Primary cutaneous actinomycosis on the chest wall
Vandana Mehta MD DNB, C Balachandran
Dermatology Online Journal 14 (8): 13

Department of Skin and STD, Kasturba Medical College, Manipal, Karnataka, India.


Actinomycosis is a chronic suppurative granulomatous infection caused by Actinomyces israelli. Primary cutaneous actinomycosis is rare and the diagnosis requires a high index of clinical suspicion. We report one such case of primary cutaneous actinomycosis on the chest wall of a healthy young woman.


Actinomycosis is a chronic suppurative granulomatous infection caused by the Gram-positive slow growing microaerophilic bacterium Actinomyces israelli. It was first reported in humans by Israel in 1878 and in 1891 Wolff and Israel were successful in culturing the microorganism [1]. It may involve virtually any organ of the body and there are five main clinical types described, depending on the primary site of involvement: cervicofacial, thoracic, abdominal, pelvic, and primary cutaneous. Primary cutaneous actinomycosis is rare and the diagnosis requires a high index of clinical suspicion. We report one such case of primary cutaneous actinomycosis on the chest wall of a healthy young woman.

Case Report

Figure 1
Figure 1. Clinical photograph showing the erythematous nodules discharging pus

A 30-year-old woman presented to us with multiple erythematous swellings discharging pus on the left side of the chest for 1½ years. At the onset there was only a single erythematous nodule, which suppurated spontaneously. Progressively, multiple such nodules developed in the vicinity discharging pus and blood. There was no history of fever, cough, chest pain, hemoptysis, weight loss, or trauma prior to the development of lesions nor any similar lesions elsewhere. She had been treated with oral and intravenous antibiotics in the past with only partial response. Clinical examination revealed a large 10 x 10cm, indurated, erythematous plaque on the left chest studded with multiple erythematous nodules and areas of scarring (Fig. 1). There was no regional lymphadenopathy. Based on the history and clinical findings a differential diagnosis of tuberculosis, deep fungal infection, and actinomycosis was considered. All the routine hematological and biochemical investigations including chest X-ray were normal. A test for hepatitis B (HBsAg) and ELISA for HIV were negative.

Figure 2Figure 3
Figure 2. Photomicrograph showing the polymorphous inflammatory infiltrate.JPG inflammatory infiltrate (x20)
3. Photomicrograph showing multiple abscess cavities in the dermis (x100)

Figure 4
Figure 4. Photomicrograph of the PAS stain showing the actinomycotic colony (x200)

Examination of purulent material revealed sulfur granules. Microbiological culture of a skin biopsy specimen for both aerobic and anaerobic bacteria failed to reveal any growth. Culture for M. tuberculosis and fungi was negative. A lesional biopsy showed multiple abscesses in the dermis with the presence of abundant lymphocytes, plasma cells, neutrophils, and macrophages with one abscess showing an actinomycotic colony. Gram staining and staining with PAS also showed actinomycotic colonies suggestive of cutaneous actinomycosis (Figs. 2, 3, 4).

The diagnosis of cutaneous actinomycosis was made. Our patient received oral and IV penicillin for a few months at another institution. She had improved, but desired an alternative treatment. She was started on oral azithromycin 500mg once daily in combination with dapsone 100mg at night. She improved notably over the first four months of this therapy. The patient has now continued on this regimen for one year with regular follow-up and the lesions are continuing to flatten and regress.


Actinomyces spp. are normal commensals of the human oropharynx, gastrointestinal tract, and genitourinary tract. Fourteen species have been characterized to date of which six are thought to be pathogenic in humans. Actinomyces israelli is most commonly incriminated in human disease [2]. Actinomycosis is invariably acquired by endogenous implantation into deep tissues where anaerobic conditions prevail. Puncture wounds, compound fractures and dental extractions are some of the possible routes of infection. The belief that infection may be from endogenous sources is further confirmed by the fact that A. israelli has never been demonstrated in soil, plants, or any other object outside the body. Cutaneous lesions occur by direct contiguous extension from an underlying primary focus or by hematogenous dissemination during the septicemic phase of the infection, in which case there are often multiple lesions [3]. Primary cutaneous actinomycosis is uncommon and has an association with trauma and human bites. It should be diagnosed only when the presence of a deeper form of infection is excluded. Very few such cases have been reported in the literature. However, culture confirmation of the diagnosis is a rarity and is not achieved in most cases [4, 5, 6, 7]. In our patient there was no history of trauma so the exact pathogenesis remains unclear. Thoracic actinomycosis usually manifests as a slowly progressive pulmonary or mediastinal mass, sometimes with draining chest wall sinuses [8]. The most common symptoms are fever, cough, pleuritic chest pain, hemoptysis, or weight loss. In our case neither the clinical nor radiological features were suggestive of underlying pulmonary involvement.

Actinomyces israelli is sensitive to antibiotics that are effective against Gram-positive organisms such as penicillin, sulfonamides, streptomycin, tetracyclines, erythromycin, and rifampicin, but high doses of long term penicillin is the treatment of choice. In severe cases 12-24 million units of crystalline penicillin are administered intravenously every 12 hours for several weeks. This is followed by wide surgical excision of the infected tissue. The patient may then be switched to PO Penicillin VK (500mg every 6 hours) for 6-12 months depending upon response [9, 10, 11]. Amoxicillin/Clavulanate (Augmentin) has also been administered (500mg PO every 8 hours). However, our patient had a good response to a combination of azithromycin and dapsone.


Cutaneous actinomycosis manifesting with nodular lesions that tend to form fistulae needs to be differentiated from cutaneous tuberculosis, deep fungal infections (including sporotrichosis), and nocardiosis. Diagnosis is based on identification of characteristic sulfur granules in whole pus, histological staining, and preferably also by a positive culture.


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