Diagnosis: ABPA
(Allergic BronchoPulmonary Aspergillosis)

Radiologic Findings

Chest radiograph shows an ovoid increased density in right perihilar region.

 CT scans show a well-defined, ovoid, lobulating mass showing branching structures, which manifests persistent low-attenuation on contrast-enhanced CT scans.


 On close observation, a thin, curvilinear air-meniscus sign is noted (arrows), representing focal bronchiectasis filled with mucus, fungus ball, neoplasm, or whatever.

 

 

 

 

 

 

On expiratory, delayed thin-section CT scan,
air-trapping is noted in posterior segment of right upper lobe (oval), suggestive of stenosis of the proximal airway.

 

Brief Review

  Pulmonary disorders associated with hypersensitivity to fungus include
 
ABPA, extrinsic asthma, extrinsic allergic alveolitis.
  Two latter conditions occur much less frequently than ABPA.
  In contrast to ABPA, there is no colonization or proliferation of fungus in the airway.
  ABPA occurs almost exclusively in asthmatic patients.

  Pathologically,
the central bronchi are distended with thick mucus, admixed with cellular debris and eosinophils.
  The bronchial wall shows inflammatory cell infiltrate without evidence of fungal invasion.
  An eosinophilic pneumonia may be seen in the surrounding lung parenchyma (1).

  Recently, it has been demonstrated that
  
Aspergillus fumigatus releases a chymotrypsin-like proteinase which causes direct epithelial cell damage (2).
  Patients have symptoms including wheezing, fever, cough, pleuritic pain, and expectoration of typical mucus plugs.

  On thin-section CT,
  the presence of proximal saccular bronchiectasis is considered virtually pathognomonic for ABPA.  
  Impacted bronchi may appear as gloved finger, Y, V, toothpaste-like opacity,
  which may be transient or remain stable for months.
  Mucoid impaction is commonly seen in patients with cystic fibrosis.
  In one study of 100 cases of cystic fibrosis, approximately 10% of patients had ABPA (3).

  Among major criteria for diagnosis of ABPA including
  
asthma,
  peripheral eosinophilia,
  proximal bronchiectasis,
  pulmonary infiltrates,
  elevated serum IgE levels,
  IgG precipitins,
  immediate skin test reactivity to Aspergillus antigens,

  only proximal bronchiectasis is considered specific.
  The diagnosis is certain if all seven criteria are present and still very likely if six of seven are present.

  In one study (3), cylindrical bronchiectasis was the only type found in the non-ABPA asthmatics, whereas more severe bronchiectatic changes were detected in patient with ABPA and the finding of bronchiectasis was thought to represent advanced disease which mandate aggressive corticosteroid therapy.
 

 

References

1. Fraser RG, Pare JAP, Pare PD, Fraser RS, Genereux GP. Infectious disease of the lungs. In: Fraser RG, ed. Diagnosis of Disease of the chest. 3rd ed. Philadelphia, Pa: Saunders, 1989;996-1007
2. Robinson BW, Venaille TJ, Mendis AH, McAleer R. Allergens as proteinase: an Aspergillus fumigatus proteinase directly induces human epithelial cell detachment. J Allergy Clin Immunol 1990; 86:726-731
3. Neeld DA, Goodman LR, Gurney JW, Greenberger PA, Fink JN. Computerized tomography in the evaluation of allergic bronchopulmonary aspergillosis. Am Rev Respir Dis 1990; 142:1200-1205
 


The following comments of Dr. Ivan Pilate from Belgium contain many important differential diagnoses,
which also should be considered in this case.

Dear Dr. Kim,

About case 158:

Branching opacities without contrast enhancement, with air-trapping in a young, asthmatic patient.

Asthmatic patients can have ectatic bronchi.
I think this is a case of mucoid impaction in an ectatic bronchus, with or without ABPA.
Less likely is a mycetoma in an ectatic bronchus (filling the whole cavity).

We have to exclude underlying diseases:

1. Congenital abnormalities: - especially bronchial atresia;
- lung sequestration is another possibility, but less likely in this location.

2. Obstruction from tumor : - endobronchial tumors like carcinoid, hamartoma or lipoma ;
- adenoid cystic carcinoma and mucoepidermoid carcinoma : both can be slow-growing (with development of mucus plugs) and can simulate asthma.

3. Obstruction from foreign body.

I thank you,

Dr. Ivan Pilate
Stedelijk OLV-Ziekenhuis Mechelen, Belgium

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