Thoracic Actinomycosis: A Rare Cause of Pleural Thickening

Our plain-English summary of Thoracic Actinomycosis: A Rare Cause of Pleural Thickening, by E. Shum, J. Muhandiramge, J. Finn, et al (Respirology Case Reports, 2026).

The study

• Authors: E. Shum, J. Muhandiramge, J. Finn, J. Zhu, R. Cameron, R. O'Donnabhain
• Journal: Respirology Case Reports
• Published: 2026;14(4):e70451
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A middle-aged man presented with an indolent growth on his chest wall, features of sepsis, and constitutional symptoms. He was subsequently found to have raised inflammatory markers and pleural thickening on imaging which, coupled with a history of asbestos exposure, was concerning for malignancy. While there was clinical improvement with empirical intravenous penicillin antibiotics, the diagnosis was not certain until an excisional biopsy of the mass was performed, with histopathology showing Splendore Hoeppli material ('sulfur granules') leading to the diagnosis of an Actinomyces infection. The diagnosis allowed for appropriate management with a prolonged course of antibiotics, resulting in complete resolution of symptoms. This case highlights the importance of investigation for atypical infection in patients with pleural thickening, particularly in those with risk factors such as drug use.

© 2026 The Author(s). Respirology Case Reports published by John Wiley & Sons Australia, Ltd on behalf of The Asian Pacific Society of Respirology.

In plain English

This was a case report describing one patient, a 47-year-old man. The authors are based at Austin Hospital in Melbourne, Australia. He had a painful, growing chest wall lump, fevers, a rash and 15 kg of weight loss, with raised inflammatory markers. He reported significant past asbestos exposure from playing with it as a child. The article does not name a fiber type. He also injected drugs and smoked marijuana through a water pipe. A CT scan showed a mass around the lower right ribs and pleural thickening. Because of his asbestos history and pleural changes, mesothelioma was a key possibility. A needle biopsy showed no tumour and no organisms. A surgical (excisional) biopsy found 'sulfur granules'. Together with his rapid improvement on intravenous antibiotics, this led to a presumptive diagnosis of actinomycosis, a bacterial infection. The authors thought it likely came from contaminated water in his water pipe. He started oral amoxicillin, planned for at least 6 months, and by phone one year after treatment reported his symptoms had resolved. The authors concluded that patients with pleural thickening should also be investigated for atypical infection, particularly those with risk factors.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report (single patient)
• Who was studied: One 47-year-old man transferred from a regional hospital to a metropolitan hospital in Australia (authors at Austin Hospital, Melbourne). He had untreated hepatitis C, injected drugs, smoked marijuana via a bong, and worked as a poultry technician.
• Exposure: Self-reported significant previous asbestos exposure from playing with it as a child; no fiber type, product or dose is given. Other exposures noted were intravenous heroin use and marijuana smoked through a water pipe.
• Main results:
  • CT chest showed mass-like soft tissue around the lower right ribs, plus medial pleural thickening and a reactive pericardial effusion.
  • The presentation was considered highly suspicious for mesothelioma because of his previous asbestos exposure and pleural thickening.
  • An ultrasound-guided core biopsy of the chest wall mass showed no micro-organisms on staining and no neoplastic process.
  • An excisional biopsy showed colonies of organisms surrounded by Splendore Hoeppli material ('sulfur granules').
  • The patient had a marked symptomatic response to intravenous amoxicillin/clavulanic acid, given for eight days in total.
  • A presumptive diagnosis of pulmonary actinomycosis with extrapulmonary dissemination was made. The likely source was thought to be contaminated water from his water pipe.
  • He was started on oral amoxicillin 1 g three times daily, planned for at least 6 months. He did not attend further clinic appointments or imaging, but reported resolution of symptoms on phone follow-up one year after treatment.
• The authors' conclusion: The authors concluded that the case highlights the importance of investigating concurrently for atypical infection such as actinomycosis in patients with pleural thickening, particularly when they have risk factors for infection.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Thickening, Asbestos Exposure, Biopsy, Histopathology.

Related studies

• Causes of pulmonary impairment in asbestos-exposed individuals with diffuse pleural thickening — S.T. Kee, G. Gamsu, et al. (1996)
• Computer-assisted diagnosis for early stage pleural mesothelioma: towards automated detection and quantitative assessment of pleural thickening from thoracic CT images — K. Chaisaowong, T. Aach, et al. (2007)
• Diffuse pleural thickening and thoracic contraction: An indistinguishable case from malignant pleural mesothelioma — Y. Tada, M. Tagawa, et al. (2020)
• Peribronchiolar metaplasia: a common histologic lesion in diffuse lung disease and a rare cause of interstitial lung disease: clinicopathologic features of 15 cases — J. Fukuoka, T.J. Franks, et al. (2005)
• Primary malignant pericardial mesothelioma - a rare cause of pericardial effusion and consecutive constrictive pericarditis: a case report — T. Butz, L. Faber, et al. (2009)
• Epithelioid angiosarcoma: A rare cause of pericarditis and pleural effusion — U. Durani, A. Gallo de Moraes, et al. (2018)

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