Pulmonary nocardiosis

Changed by Amir Rezaee, 22 Feb 2016
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Pulmonary nocardiosis (PN) is an infrequent but severe opportunistic infection that is caused by Nocardia spp. It commonly presents as a subacute or chronic suppurative disease 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.

Epidemiology

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. 

Pathology

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

Distribution

TheirThere may be an increased upper zonal predilection 1.

Radiographic features

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 film / CT

There are several reported radiographic patterns which include

  • lobar or multilobar consolidation
    • some reports suggest that this isprobably the predominant feature 4
    • focal areas of decreased attenuation may be present within consolidated lung which likely reflectingreflect abscess formation
    • cavitation in 30%
  • solitary lung masses and/or nodules
  • reticulonodular infiltrates 9
  • mediastinal or hilar lymphadenopathy is not a feature of nocardiosis

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

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

The temporal progression of radiographic radiographic abnormalities tendtends to be slow.

Different spread patterns have givegiven 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

Treatment and prognosis

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

Differential diagnosis 

On imaging it can sometimes mimic:

  • -<p><strong>Pulmonary nocardiosis (PN)</strong> is an infrequent but severe infection that is caused by <em>Nocardia spp</em>. It commonly presents as a subacute or chronic suppurative disease.</p><h4>Epidemiology</h4><p>The condition is rare in general. Immunocompromised patients, particularly those with impaired cell-mediated immunity related to AIDS and transplantation may be particularly prone.</p><p>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 <sup>2</sup>. </p><h4>Pathology</h4><p>It is most commonly caused by <em>Nocardia asteroides</em> which is a gram positive bacterium. Other less common strains include <em>Nocardia farcinica</em> and <em>Nocardia otitidiscaviarum </em><sup>3</sup>. It is usually acquired by direct inhalation of contaminated soil.</p><h5>Distribution</h5><p>Their may be an increased upper zonal predilection<sup> 1</sup>.</p><h4>Radiographic features</h4><h5>Plain film / CT</h5><p>There are several reported radiographic patterns which include</p><ul>
  • +<p><strong>Pulmonary nocardiosis (PN)</strong> is an infrequent but severe opportunistic infection that is caused by <em>Nocardia spp</em>. 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.</p><h4>Epidemiology</h4><p>The condition is rare in general. Immunocompromised patients, particularly those with impaired cell-mediated immunity related to AIDS and transplantation may be particularly prone.</p><p>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 <sup>2</sup>. </p><h4>Pathology</h4><p>It is most commonly caused by <em>Nocardia asteroides</em> which is an aerobic gram positive weakly acid-fast bacterium distributed worldwide in soils. Other less common strains include <em>Nocardia farcinica</em> and <em>Nocardia otitidiscaviarum </em><sup>3</sup>. It is usually acquired by direct inhalation of contaminated soil.</p><h5>Distribution</h5><p>There may be an increased upper zonal predilection<sup> 1</sup>.</p><h4>Radiographic features</h4><p>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.</p><h5>Plain film / CT</h5><p>There are several reported radiographic patterns which include</p><ul>
  • -<li>some reports suggest that this is predominant feature <sup>4</sup>
  • +<li>probably the predominant feature <sup>4</sup>
  • -<li>focal areas of decreased attenuation may be present within consolidated lung which likely reflecting abscess formation</li>
  • +<li>focal areas of decreased attenuation may reflect abscess formation</li>
  • +<li>cavitation in 30%</li>
  • -</ul><p>Other accompanying features which are non specific on their own include</p><ul>
  • -<li>
  • -<a href="/articles/pleural-effusion">pleural effusion</a>: can be focal</li>
  • +<li>mediastinal or hilar lymphadenopathy is <strong>not</strong> a feature of nocardiosis</li>
  • +</ul><p>Other accompanying features which are non-specific on their own include</p><ul>
  • +<li><a href="/articles/pleural-effusion">pleural effusion</a></li>
  • -<a title="Lung cavitating lesions" href="/articles/pulmonary-cavity">lung cavitating lesions</a>: may occur in up to a 3<sup>rd </sup>patients<sup> 4</sup>
  • +<a href="/articles/pulmonary-cavity">lung cavitating lesions</a>: may occur in up to a 3<sup>rd </sup>patients<sup> 4</sup>
  • -<li>chest wall invasion: can lead to <a href="/articles/empyema-necessitans">empyema necessitans</a><sup> 4,5</sup>
  • +<li>
  • +<a href="/articles/empyema-necessitans">empyema necessitans:</a> can lead to chest wall invasion <sup>4,5</sup>
  • -</ul><p>Those with immunodeficiency may show more cavitating lesions and multiple nodules <sup>6</sup>.</p><p>The temporal progression of radiographic abnormalities tend to be slow.</p><p>Different spread patterns have give varying features</p><ul>
  • +</ul><p>Those with immunodeficiency may show more cavitating lesions and multiple nodules <sup>6</sup>.</p><p>The temporal progression of radiographic abnormalities tends to be slow.</p><p>Different spread patterns have given varying features</p><ul>
  • -</ul><h4>Treatment and prognosis</h4><p>The usual treatment of choice includes sulphonamides (cotrimoxazole) and, more recently, TMP-SMX. With certain complications, surgical drainage may be required. The prognosis can vary with those with disseminated nocardiosis having morality rates upt o 40%.</p><h4>Differential diagnosis </h4><p>On imaging it can sometimes mimic</p><ul>
  • -<li><a href="/articles/lung-cancer-3">lung cancer</a></li>
  • +</ul><h4>Treatment and prognosis</h4><p>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. </p><h4>Differential diagnosis </h4><p>On imaging it can sometimes mimic:</p><ul>
  • +<li>
  • +<a href="/articles/lung-cancer-3">lung cancer</a>: in particular SCC with cavitation</li>
Images Changes:

Image 2 X-ray (Frontal) ( update )

Caption was changed:
Case 2: on CXR

Image 3 CT (lung window) ( update )

Caption was changed:
Case 2: on CT

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