What Is Responsible for This Woman’s Chronic Cough?
Author: William Yaakob, MD
Citation: Consultant. 2016;56(1):61-63.
A 53-year-old woman presents to your office with a chronic cough of approximately 3 months’ duration. At the onset, there was no sputum production. However, in the past few weeks, she has felt progressively ill. In the past 2 weeks, she has had increased sputum production and occasional fevers in the evening. She would like some relief from this chronic cough.
History
Her past medical history is significant for allergies and asthma, for which she has been treated intermittently with β2 agonists, but has never required hospitalization. She is otherwise in good health.
Physical Examination
Her vital signs include a respiratory rate of 16 breaths/min, heart rate of 86 beats/min, blood pressure of 135/80 mm Hg, and temperature of 37.2°C. The physical examination reveals a thin woman in mild respiratory distress, with intermittent coughing while trying to suppress some of the coughing. She is able to walk without difficulty. The examination of the chest reveals decreased breath sounds at the lung bases, right greater than left. Findings of auscultation of the heart are within normal limits. There is no palpable adenopathy in the neck, axillary regions, or inguinal regions.
Laboratory Tests
Two views of the chest are ordered in further investigation (Figures 1 and 2). These radiographhs demonstrate regions of nodularity in the lungs. This is most prominent in the region of the right middle lobe but is also identified in the right upper lobe and right lower lobe. This is present to a lesser degree at the left lung base and is best identified on the frontal projection. There is no evidence of pleural effusions. The cardiomediastinal silhouette is unremarkable. Magnified images of the abnormalities (Figures 3 and 4) demonstrate a nodular tree-in-bud appearance with regions of “tram-tracking.”
What’s Your Diagnosis?
A. Metastatic thyroid cancer
B. Miliary tuberculosis
C. Mycobacterium avium intracellulare infection of the lungs
D. Varicella-zoster infection
E. Primary lung cancer
Answer on next page
Answer: Mycobacterium avium-intracellulare infection of the lungs
Metastatic thyroid cancer to the lungs can give a nodular, miliary pattern of disease. However, for a diagnosis of metastatic thyroid cancer, it would be expected to have a prior history of thyroid cancer, which is not present in this case. Metastatic thyroid cancer to the lungs is expected to be more evenly distributed throughout the lungs, favoring the lung bases as it would be spread hematogenously. Physical examination findings of the neck were again negative. This is unlikely to represent the diagnosis.
Miliary tuberculosis can also present with a nodular pattern of disease within the lungs. However, if the chest radiographs reveal miliary tuberculosis, this typically represents an advanced disease. One would expect the patient to be acutely ill and be unable to stand. While this may be present for a long time, acute miliary tuberculosis is unlikely to present for several months. This is difficult to exclude and does need to be considered. In this case, there is no evidence of cavitation. There is a lower lobe predominance, which makes Mycobacterium tuberculosis less likely but again very difficult to exclude.
Varicella zoster can present as miliary disease in the lungs. Patients are typically immunocompromised. They can present with multiple lung nodules and typically have a halo of ground-glass opacity on computed tomography (CT) scans. It is not associated with bronchiectasis. In this case, the nodules were very concentrated, making this option less likely, and there are no other manifestations of varicella infection.
Primary lung cancer would be expected to have a single large nodule. This is often associated with adenopathy, which is not demonstrated in this case. This would be extremely unusual for a primary lung cancer.
M avium intracellulare (MAI) infection is the most likely diagnosis. This typically occurs in elderly women and is thought to be brought on by voluntary cough suppression, which creates a layering of secretions in the lungs to provide a medium for the infection. Additionally, there is often bronchiectasis in this group, particularly with a history of asthma. Often these symptoms occur for prolonged periods. This diagnosis best fits the chest radiographic pattern and the CT pattern.
Diagnostic Imaging
CT images (Figures 5-7) confirmed the regions of nodularity and demonstrated the tram-tracking visualized on the chest radiographs to represent regions of bronchiectasis. The nodularity is a tree-in-bud distribution, representing pus in the acini as well as bronchioles.
M avium and M intracellulare are 2 different species of mycobacteria. They are extremely difficult to differentiate from one another, and therefore the combined name of MAI is often used. MAI infection can occur in patients who are immunocompromised. MAI lung disease can occur in otherwise healthy patients. It is often associated with bronchiectasis and seen in elderly women. The tree-in-bud appearance as identified on the CT and chest radiograph are classic for bronchiolitis/infectious involvement of the lungs and can often suggest MAI, although other infectious etiologies should be considered.
Pulmonary MAI infection is associated with chronic lung diseases, such as chronic obstructive pulmonary disease, chronic bronchitis, and bronchiectasis.
MAI infection is typically treated with 2 or 3 antimicrobials for at least 12 months.
William Yaakob, MD, is a board-certified radiologist working in Tallahassee, Florida.