Authors Daniel G. Dunlap, MD1; Jared Chiarchiaro, MD1 Affiliations: 1Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA
Case
A previously healthy, 67-year-old male presents with dyspnea on
exertion and an abnormal chest radiograph. The patient reports 1.5
years of progressively worsening dyspnea on exertion, now requiring
supplemental oxygen with activity. CT chest demonstrates the following (Figure 1A and IB):
Figure 1A:
Figure 1B:
Question
What is the clinician’s next step in evaluation?
A. Bronchoscopy with transbronchial biopsies B. VATS biopsy C. Obtain further history D. Prednisone burst E. Referral for lung transplantation
Answer
Answer: C. Obtain further history
Discussion
Obtaining a complete social and occupational history is critical when
evaluating patients with interstitial lung disease (ILD). This
patient’s CT chest demonstrates traction bronchiectasis and
honeycombing, consistent with a usual interstitial pneumonia (UIP)
pattern of fibrosis. UIP is the typical histopathologic finding in
idiopathic pulmonary fibrosis (IPF), but may also be seen in a myriad of
other end-stage pulmonary diseases. This patient lives on a farm and
frequently works in a silo. Furthermore, his symptoms flare when
working on the farm and improve when he limits his exposures. Thus, he
was diagnosed with hypersensitivity pneumonitis (HP).
Hypersensitivity pneumonitis, also known as extrinsic allergic
alveolitis, refers to inflammation of the alveoli, bronchioli, and
alveolar interstitium because of a delayed allergic reaction to inhaled
organic particles. Hypersensitivity pneumonitis is a clinical diagnosis
and can be a challenging diagnosis to make. Both imaging and blood
work can be variable and identification of the precipitating antigen is
frequently never achieved. In fact, there is no consensus regarding
diagnostic criteria for this disease (1, 2). Though there are no formal
guidelines, multidisciplinary discussion and bronchoscopy with biopsy
often play an important role in diagnosis, particularly when imaging is
not typical for UIP.
Hypersensitivity pneumonitis comes in three stages: acute, subacute,
and chronic, all of which have a different set of symptoms and
radiographic findings. Acute HP generally occurs a few hours after
exposure and is characterized by flu-like symptoms including fever,
cough, and wheezing. CT imaging may be normal or could demonstrate
ground glass opacities consistent with pneumonitis. Subacute HP results
from repeated exposures to low-level antigens. Patients usually
present with insidious onset of malaise, dry cough, and dyspnea over a
period of weeks to months. Imaging generally consists of ground glass
opacities, diffuse micronodules, and mosaicism with areas of focal
air-trapping (Figure 2). Chronic HP is the result of
unrecognized/untreated acute and subacute episodes. Symptoms of
dyspnea, cough and weight loss are common and imaging in advanced cases
is often indistinguishable from IPF or fibrotic non-specific
interstitial pneumonia (3).
Identification of HP is critical, as both treatment and prognosis are
substantially different from IPF and other interstitial lung disease.
The primary treatment modality is antigen avoidance, though this is not
always feasible and an inciting antigen cannot be identified in over
50% of cases (4). The next step in treatment consists of
immunosuppression, which begins with systemic corticosteroids for acute
management. If there is response to corticosteroid, then the goal is to
transition to a steroid-sparing medication such as azathioprine or
leflunomide with the goal of slowing or preventing progression of
disease. Immunosuppression is less likely to be helpful in advanced
disease with fibrosis, and in these patients prognosis is quite poor and
similar to that seen in individuals with IPF (5).
Figure 2:
References
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