A 36-year-old man is brought to the emergency department after waking up with dyspnea, nonproductive cough, fever, and malaise. He had been feeling well prior to these symptoms and has no chronic medical problems. The patient and his wife are on vacation in Florida and are staying in an "old and dusty" rental house. Last night they went to a bar and then relaxed in a hot tub.
Temperature is 38.9 C (102 F), blood pressure is 144/89 mm Hg, and pulse is 104/min. Pulse oximetry is 89% on room air. Chest examination reveals bilateral fine crackles. There are no skin rashes.
Laboratory results are as follows:
Liver function tests are normal. Chest x-ray reveals mildly increased interstitial markings in the middle and lower lung fields bilaterally.
Which of the following is most likely responsible for this patient's current symptoms?

Question

A 36-year-old man is brought to the emergency department after waking up with dyspnea, nonproductive cough, fever, and malaise.  He had been feeling well prior to these symptoms and has no chronic medical problems.  The patient and his wife are on vacation in Florida and are staying in an "old and dusty" rental house.  Last night they went to a bar and then relaxed in a hot tub.
Temperature is 38.9 C (102 F), blood pressure is 144/89 mm Hg, and pulse is 104/min.  Pulse oximetry is 89% on room air.  Chest examination reveals bilateral fine crackles.  There are no skin rashes.
Laboratory results are as follows:
 Liver function tests are normal.  Chest x-ray reveals mildly increased interstitial markings in the middle and lower lung fields bilaterally.
Which of the following is most likely responsible for this patient's current symptoms?

Quizplus · Accepted Answer

Mycobacterium avium complex (MAC) is a group of free-living nontuberculous mycobacteria that are ubiquitous in the environment. Humans acquire the organism primarily via inhalation of aerosolized municipal water, but transmission can also occur through contaminated soil, food, and animals (eg, birds). Most healthy individuals exposed to MAC have little risk of infection. However, disseminated disease can occur in patients with severe immunodeficiency (eg, AIDS), and chronic pulmonary infections can occur in those with underlying lung disease or in nonsmoking women age >50. MAC can also induce a hypersensitivity pneumonitis ("hot tub lung"), particularly in those with recent exposure to contaminated hot tub water. Manifestations include an acute, flu-like illness with dyspnea, cough, malaise, and fever. Most cases are self-limited and resolve with close observation, supportive care, and avoidance of hot tub exposure. However, if symptoms worsen or persist, a short course of prednisone is often indicated. (Choice A) Although infection with Chlamydia psittaci can cause similar manifestations, most patients have severe headaches and a history of close contact with birds, making the diagnosis less likely in this patient. (Choice C) Pseudomonas infections associated with hot tub use usually present as folliculitis, not pneumonia. In addition, Pseudomonas pneumonia would be more likely to develop over days (not hours) and be associated with a lobar infiltrate (not patchy interstitial infiltrate). folliculitis (Choice D) Pneumonia caused by Staphylococcus aureus occurs primarily after influenza infection. Most cases are marked by lobar (or multilobar) consolidation, not interstitial infiltrates. (Choice E) Although Streptococcus pneumoniae is the most common cause of community-acquired pneumonia, patients typically have productive cough and a lobar (not interstitial) infiltrate. Educational objective: Patients with hot tub/spa exposure are at risk for Mycobacterium avium complex infection and can present with hypersensitivity pneumonitis ("hot tub lung"). Manifestations are often acute and resemble an influenza infection. Most cases are self-limited and resolve with supportive care; a short course of prednisone can be used if symptoms do not resolve. __________ References: Hot tub lung mimicking classic acute and chronic hypersensitivity pneumonitis: two case reports. (http://www.ncbi.nlm.nih.gov/pubmed/17885696) Hypersensitivity pneumonitis-like granulomatous lung disease with nontuberculous mycobacteria from exposure to hot water aerosols. (http://www.ncbi.nlm.nih.gov/pubmed/17384775)

A 36-Year-Old Man Is Brought to the Emergency Department After