Mark Crislip, MD

Disclosures

September 30, 2011

Differential Diagnosis

It is not unheard of for all of the infections listed above to be mistaken for malignancies, because cancer is common and these infections are rare.

Actinomycosis is notable for eroding through, rather than along, tissue planes. The patient's recent dental work could have provided an opportunity for aspiration of this microorganism. About 15% of actinomycosis will involve the chest wall.[1] Actinomycosis can also mimic bowel and uterine cancer and is associated with prolonged intrauterine device use.[2]

Histoplasmosis is found throughout the Mississippi River Valley and is a common cause of pulmonary infection. Histoplasma species does not usually invade into tissues, and the more common manifestation (when it is mistaken for a malignancy) is a pulmonary nodule that is positive on PET scan.[3] PET scans can be positive for granulomatous infections as well as for tumors and may mislead clinicians.[4]

Aspergillus species is ubiquitous in the environment and can cause invasive disease in ostensibly immunologically intact patients, although this is rare.[5] Usually, it leads to cavitary disease in the lung rather than a mass, perhaps as a result of its predilection for invading tissues and causing thrombosis or infarction.

Tuberculosis can present with a mass and hemoptysis, but when it erodes though the chest wall, it is part of an empyema necessitans and virtually always causes cavities in the lung.[6]

Other fungi that can be mistaken for a pulmonary malignancy include cryptococcosis and coccidiomycosis, which can cause "round" pneumonias that appear to be malignant nodules on CT and chest radiograph.

The pathology and subsequent cultures of this patient's infection demonstrated blastomycosis, which has also been mistaken for malignancy.[7]

Discussion

Blastomycosis is found in the soil of the Mississippi River Valley, the Ohio River Valley, and the St. Lawrence Seaway. It can also be found in the mountains of Tennessee.[8] To acquire blastomycosis, people need to have their noses in the dirt, inhaling dust, which this patient essentially did getting to the base of the dams. Blastomycosis is a bigger problem in dogs, which tend to sniff the ground. There was a recent urban outbreak in Indianapolis caused by summer roadwork kicking up dirt.[9] Another curious case developed after a kinkajou bite, so don't get bitten by a kinkajou.[10]

This case emphasizes the importance of an exposure history to be able to include the infection in the differential diagnosis and alert the microbiology laboratory that you would like them to try and isolate unusual pathogens.

Treatment

The treatment of blastomycosis is amphotericin followed by itraconazole. Itraconazole is the only "azole" that requires gastric acidity for absorption, but this patient was taking a proton pump inhibitor for GERD. Besides discontinuing the acid suppressant, the patient was instructed to take his medications with Coke®, which has been shown to increase the absorption and blood levels of itraconazole.[11]

Does it have to be Coke? Coke is the only soda for which there are data, but the pH of various soft drinks is as follows:

  • Coke: 2.44

  • Pepsi®: 2.46

  • Dr. Pepper®: 2.93

  • Sprite®: 2.88

  • Mountain Dew: 3.23

  • Mug Root Beer®: 4.06[12]

With the possible exception of Mug Root Beer, these drinks should all have the same beneficial effect on itraconazole absorption. No data are available for beer, although the pH of most beers is between 3.90 and 4.20, suggesting that beer may not be as useful as soda, at least as far as itraconazole absorption is concerned.

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