What is the diagnosis

RADIOLOGIC DIAGNOSIS

What is the diagnosis

Jorge Kavakama^I; Jaime Ribeiro Barbosa^II; Nestor Müller^III

^IRadiologista de Diagnósticos por Imagem do Instituto do Coração-InCor do HCFMUSP, São Paulo, SP

^IIInstituto de Radiologia de Presidente Prudente

^IIIVancouver General Hospital, Vancouver, BC, Canadá

45 year old man, asymptomatic.

• 28 pack-year smoker.

• Worked for seven years in an asbestos mine.

• Screening radiograph requested by the employer.

The aim of this section is to stimulate a practical approach to the diagnosis based on the clinical information and the radiologic findings. We invite all our readers to participate. You may send your opinion by filling out a form that can be found at the site www.jornaldepneumologia.com.br, or by e-mail ([e-mail]). Do not forget to identify yourself; we will publish the names of the individuals who make the correct diagnosis. The images shown above are the key ones for the diagnosis. Further details can be found at jornaldepneumologia.com.br. The diagnosis of this case will be published in the next issue of the journal.

Diagnosis of previous case

J Pneumol 2003;29(5):332

Hypersensitivity pneumonitis (extrinsic allergic alveolitis)

Figure

HIGH-RESOLUTION COMPUTED TOMOGRAPHY (HRCT )

Diffuse ground glass opacities.

Poorly defined centrilobular nodules.

Occasional branching opacities in a "tree-in-bud" pattern.

Comments

Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is an immunologically mediated disease caused by the inhalation of various antigens. The vast majority of antigens originate from organic dusts of vegetable or animal origin. A small percentage of cases of HP have been described following inhalation of chemicals.

The best known causes of HP are inhalation of termophilic actinomycetes (first described in "farmer’s lung") and inhalation of proteins from bird secretions ("bird fancier’s lung"). However, a number of other organic antigens have been shown to result in HP.

Acute stage: The acute stage of HP is characterized by the development of respiratory symptoms a few hours after exposure to a large amount of antigen. The chest radiograph may be normal or demonstrate extensive symmetric bilateral airspace consolidation.

Subacute stage: This is the most commmon form of presentation with slowly progressive dyspnea over several weeks or months.

High-resolution CT has been shown to be very helpful in the evaluation of patients in the subacute stage. The characteristic high-resolution CT findings consist of poorly defined centrilobular nodules measuring less than 5 mm in diameter

Another common finding on high-resolution CT is the presence of diffuse bilateral ground-glass opacities, often associated with focal areas of decreased attenuation and decreased vascularity and lobular areas of air trapping on expiratory high-resolution CT. Some patients have only centrilobular nodules, some have only ground glass opacities, but the majority has both findings.

It should be noted that in some patients with subacute HP the high-resolution CT may show only subtle abnormalities or be normal.

Chronic stage: The chronic stage is characterized by the presence of fibrosis resulting in a reticular pattern, traction bronchiectasis and architectural distortion. Because of recurrent exposure to antigen the patients with fibrosis secondary to HP usually have centrilobular nodules and ground glass opacities in association with the reticular pattern.

Diagnosis of hypersensitivity pneumonitis in the current patient was proven at surgical biopsy.

Acknowledgment: This case, besides Drs. Jaime Barbosa, Jorge Kavakama and Nestor Müller, had input provided by Dr. Rogério de Souza, assistant in the Division of Respirology at the HCFMUSP.

REFERENCES

• Fraser RS, Müller NL, Colman N, Paré PD. Diagnosis of Diseases of the Chest. Fourth Edition. WB Saunders Company. Philadelphia, 1999.
• Naidich DP, Muller NL, Zerhouni EA, Webb WR, Krinsky GA, Siegelman SS. Compute Tomography and Magnetic Resonance of the Thorax. Third Edition. Lippincott-Raven. Philadelphia, 1999.
• Webb WR, Muller NL, Naidich DP.High-Resolution CT of the Lung. 3^rd edition. Lippincott-Raven. Philadelphia.

Publication Dates

• Publication in this collection
  17 June 2004
• Date of issue
  Dec 2003