I recently saw a patient, Mary, with 2 nodules in a line extending from the top of her left wrist to the forearm Her prevous doctor had excised a nodule from the top of her hand in order to make a diagnosis. The biopsy showed inflammation suspicious for several different types of infections. Special stains were done looking for several types of bacteria, fungus and yeast, but all were negative. A culture from the top of one of the lesions was also negative. She had been treated with several antibiotics with no success. She has family overseas and travels to Vietnam several times a year, but had not travelled right before the nodules came out. Of note, she is an preschool teacherand has an aquarium in the classroom. She cleans the aquarium with her right hand ( the nodules were on the left)
Since infection was most likely, I did another biopsy and sent the specimen to the hospital microbiology lab for 3 different types of cultures: bacterial, fungal and acid -fast bacteria ( the family of bacteria that include tuberculosis) which need to be cultured under special conditions. After 3 weeks, the lab identified a mycobacteria ( the bacteria group that includes TB) and sent the specimen to the Mayo clinic where a type of DNA testing called PCR (polymerase chain reaction) is done to identify the species. After another three weeks the answer came,Mycobacterium Marinum, a rare species of bacteria known to grow in aquariums. The usual way of acquiring this infection is cleaning the aquarium without gloves, as our patient had been doing.
After researching the recommended antibiotic therapy, I called one of my infectious disease specialist colleagues to confirm the best approach. Since our patient is not sick, a single antibiotic, Doxycycline, over an extended course of 3-4 months is the recommended course of treatment. In the meantime, the Mayo clinic lab is testing the organism to determoine which antibiotic is likely to be most effective. That will be useful in case our initial choice of treatment is not working. Our patient will be purchasing elbow length rubber gloves for future aquarium cleaning.
In a recent study, it was found that diagnosis of mycobacterium marinum is often delayed 4- 6 months. Read more. Our patient first saw a physician in December of 2012 , presented to my practice in June of 2013 and was finally diagnosed in September. ( her biopsy appointment was delayed due to a 2 month trip to Taiwan) Physicians need to be suspicous of this condition in anyone with nodules on the hand or arm. And patients should seek a second opinion if the first doctor does not come up with an answer.
And if you own an aquarium, do use gloves for cleaning.