Mycobacterium marinum

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Mycobacterium marinum Symptoms & Signs

Bumps on the Skin

People often describe localized swollen areas on, or under, the skin as lumps or bumps. While bumps on, or under, the skin may result from conditions that give rise to a skin rash, many other conditions can result in solitary raised lumps on the skin. Infections, tumors, and the body's response to trauma or injury can all lead to lumps or bumps that appear to be located on or underneath the skin.

What is Mycobacterium marinum?

Mycobacterium marinum (M. marinum) is a slow-growing atypical mycobacterium that is commonly found in bodies of fresh or saltwater in many parts of the world. Skin infections with Mycobacterium marinum in humans are relatively uncommon and are usually acquired from contact with contents of aquariums or fish. Most infections occur following skin exposure to the bacteria through a small cut or skin scrape. The first signs of infection with M. marinum include a reddish or tan skin bump called a granuloma. Less commonly, a string or batch of the small reddish bumps crop up on the exposed body area in a classic pattern called sporotrichotic lymphangitis.

It is somewhat rare to acquire this infection from well-maintained swimming pools because of protection afforded by proper chlorination. Mycobacterium marinum does not typically grow at normal body temperature, which is why it remains localized to the cooler skin surface. Overall, diagnosis and treatment of this unusual skin infection is often delayed because of a lack of suspicion for this atypical mycobacterium versus more common bacteria like Staphylococcus.

What are other names for Mycobacterium marinum infections?

Some synonyms for Mycobacterium marinum skin infections include tropical fish granuloma, fish tank granuloma and fish tank granuloma.

How common is Mycobacterium marinum?

Although rare, infections can occur worldwide, most commonly in individuals with occupational and recreational exposure to fresh or saltwater. In the United States, infections caused by M. marinum are rare. The infection is very rare in children and is typically a disease of adults, although any person, regardless of age, may become infected.

Medically Reviewed by a Doctor on 9/12/2016

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