Pulmonary nocardiosis

Pulmonary nocardiosis is an infrequent but severe opportunistic infection that is caused by Nocardia spp. It commonly presents as a subacute or chronic unilobar or multilobar consolidation, lung nodules or masses occasionally with cavitation in an immunocompromised people with cell immunity impairment like transplant or HIV/AID patients.

The condition is rare in general. Immunocompromised patients, particularly those with impaired cell-mediated immunity related to AIDS and transplantation may be particularly prone.

Incidence rates however may have increased probably due to a combination improved laboratory detection techniques as well as greater number of individuals with impaired cellular immunity 2

It is most commonly caused by Nocardia asteroides which is an aerobic gram positive weakly acid-fast bacterium distributed worldwide in soils. Other less common strains include Nocardia farcinica and Nocardia otitidiscaviarum 3. It is usually acquired by direct inhalation of contaminated soil.

Distribution

There may be an increased upper zonal predilection 1.

Due to high rate of diffuse hematogenous spread, if diagnosis of pulmonary nocardiosis made, the brain MRI in particular would be recommended to exclude presence of cerebral abscesses. Other organs such as liver, adrenal, skin, and soft tissues can also be involved.

Plain radiograph / CT

There are several reported radiographic patterns which include

Other accompanying features which are non-specific on their own include

Those with immunodeficiency may show more cavitating lesions and multiple nodules 6.

The temporal progression of radiographic abnormalities tends to be slow.

Different spread patterns have given varying features

  • endobronchial spread
    • can occur with cavitation 
    • characterised by the presence of small centrilobular nodules, often associated with bronchial wall thickening and endobronchial debris 
  • disseminated pulmonary nocardiosis
    • consists of numerous nodules of various sizes

The usual treatment of choice includes sulphonamides and more recently TMP-SMX (cotrimoxazole). With certain complications, surgical drainage may be required. The prognosis can vary with those with disseminated nocardiosis having mortality rates up to 40%. Subtherapeutic levels of antibiotics can result in flare-ups while patients are on treatments. 

On imaging it can sometimes mimic:

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Article Information

rID: 21211
System: Chest
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:
  • Pulmonary involvement with nocardiosis
  • Pulmonary involvement with nocardia
  • Nocardia infection of the lung
  • Lung nocardiosis
  • Pulmonary nocardiosis (PN)
  • Nocardiosis of the lung

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Cases and Figures

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