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"Horse play and the Lung" - a possible cobalt effect?

Case Editor - Judd Flesch

Reviewed By Environmental & Occupational Health Assembly

Submitted by

Husam M. Abdel-Qadir

Postgraduate trainee in Internal Medicine

Toronto Western Hospital

Toronto, Canada

Marcos M Ribeiro MD

Clinical Research Fellow

Toronto Western Hospital

Toronto, Canada

William Geerts MD


Department of Medicine

University of Toronto

Toronto, Canada

Adam Wisnewski PhD

Associate Professor

Department of Internal Medicine

Yale University School of Medicine

Connecticut, USA

Susan M Tarlo M.B, B.S


Department of Medicine

University of Toronto

Toronto, Canada

Submit your comments to the author(s).


A 38-year-old female horse-farmer was referred to us with a history of respiratory symptoms beginning on the day she started to use a new, finely powdered, horse-feed supplement. She developed dyspnea immediately after exposure and later that day noted a nonproductive cough, lightheadedness, and chest discomfort. Over the following week, the cough continued and she noted mild wheezing, progressive exertional dyspnea, and upper chest tightness exacerbated by activity such as climbing one flight of stairs. These symptoms prompted her to make an emergency department visit.  She had no fever, chills, arthralgias, or hemoptysis. She was an ex-smoker for 18 months after a 7 pack-year history. Past medical history and review of systems were remarkable only for a history of childhood asthma, which was triggered by unusually high exposures to dust and horses. This required only rare short-acting bronchodilator use and had improved by the age of 12. She also had symptoms to suggest mild allergic rhinitis in the spring.

Physical Exam

Physical examination one week after the onset of her symptoms revealed no respiratory distress at rest. She was afebrile with normal vital signs, respiratory rate was 20/minute, and oxygen saturation at rest was 98% on room air. There was no clubbing or lymphadenopathy and chest examination was normal. There were no crackles or wheezes. The jugular venous pressure was not increased and cardiovascular examination was normal. A complete blood count (CBC) and differential white blood cell count (WBC) were unremarkable. A chest radiograph showed diffuse hazy opacities in the lungs bilaterally (Figure 1 and 2). She was referred for pulmonary outpatient assessment.


Figure 1: Chest radiograph 1 week after symptom onset

Figure 2: Chest radiograph 1 week after symptom onset

Figure 3: Chest CT 1 month after the onset of symptoms

Figure 4: Transbronchial biopsy

Figure 5: High resolution CT scan at 6 months

Question 1

Which of the following would be the most appropriate first step in the investigation at this time? (Review the answer to question 1 before going to question 2.)


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