Sporotrichosis is an infection of the skin caused by a fungus, Sporothrix schenckii. This fungus is related more closely to the mold on stale bread or the yeast used to brew beer than to bacteria that usually cause infections. The mold is found on rose thorns, hay, sphagnum moss, twigs, and soil. The infection is more common among gardeners, nursery workers, and farmers who work with roses, moss, hay, and soil.
Once the mold spores move into the skin, the disease takes days or even months to develop.
Causes of Sporotrichosis
Sporotrichosis usually begins when mold spores are forced under the skin by a rose thorn or sharp stick, although the infection can begin in apparently unbroken skin after contact with hay or moss carrying the mold.
More rarely, cats or armadillos can transmit the disease.
In rare cases, the fungus can be inhaled or ingested, causing infection in parts of the body other than the skin.
Sporotrichosis does not appear to be transmitted from person to person.
Symptoms of Sporotrichosis
The first symptom of sporotrichosis is a firm bump (nodule) on the skin that can range in color from pink to nearly purple. The nodule is usually painless or only mildly tender. Over time, the nodule may develop an open sore (ulcer) that may drain clear fluid. Untreated, the nodule and the ulcer become chronic and may remain unchanged for years.
In about 60% of cases, the mold spreads along the lymph nodes. Over time, new nodules and ulcers spread in a line up the infected arm or leg. These can also last for years.
In very rare cases, the infection can spread to other parts of the body, such as the bones, joints, lungs, and brain. This is more common among those with a weakened immune system. It can be difficult to treat and may be life threatening.
When to Seek Medical Care for Sporotrichosis
When to call the doctor
- If you think you might have sporotrichosis, see a doctor about diagnosis and treatment.
- If you are already being treated for sporotrichosis, contact a doctor if new sores develop or if the old ones appear to be growing.
When to go to the hospital
- Sporotrichosis in the skin or lymph nodes should not be dangerous or life threatening.
- Open ulcers can become infected with bacteria and may cause a condition known as cellulitis.
- If a rapidly expanding area of redness, pain, and warmth around the original ulcers develops, you should go to your local emergency room.
Exams and Tests for Sporotrichosis
Other infections can mimic sporotrichosis, so a doctor performs tests to confirm the diagnosis. The tests for sporotrichosis usually involve a biopsy of one of the nodules, followed by an exam of the biopsy sample under a microscope to identify the mold. Other possible infections might include:
- Bacteria related to tuberculosis or leprosy
- Other fungi and bacteria
- Noninfectious diseases such as lupus
Sporotrichosis Care at Home
No effective home care for sporotrichosis is known. Ulcers should be kept clean and covered until they are healed.
Medical Treatment for Sporotrichosis
Treatment of sporotrichosis depends on the site infected.
- Infections in the skin only: These sporotrichosis infections have traditionally been treated with a saturated potassium iodide solution. This medicine is given three times per day for three to six months until all the lesions have gone away. Skin infections may also be treated with itraconazole (Sporanox) for up to six months.
- Sporotrichosis infection in the bones and joints: These infections are much more difficult to treat and rarely respond to potassium iodide. Itraconazole (Sporanox) is often used as an initial medication for several months or even up to a year. Amphotericin is also used, but this drug can only be given through an IV. Amphotericin has more side effects and may need to be administered for many months. Surgery is sometimes needed to remove infected bone.
- Infection in the lungs: Lung infections are treated with potassium iodide, itraconazole (Sporanox), and amphotericin with varying amounts of success. Sometimes, the infected areas of the lung have to be removed.
- Infection in the brain: Sporotrichosis meningitis is rare, so information on treatment is not readily available. Amphotericin plus 5-fluorocytosine is generally recommended, but itraconazole (Sporanox) might also be tried.
Follow-up Care for Sporotrichosis
Multiple follow-up visits may be needed with a doctor to make sure sporotrichosis is disappearing. Once the disease goes away, further follow-up care is generally not needed.
The most important step in preventing sporotrichosis is preventing mold spores from entering the skin.
People who work with roses, hay, or sphagnum moss should cover any scratches or breaks in their skin. They should also wear heavy boots and gloves to prevent puncture wounds.
Outlook for Sporotrichosis
Most people who have sporotrichosis only in their skin or lymph nodes make a full recovery.
Treating a sporotrichosis infection may take several months or years, and scars may remain at the site of the original infection.
Infections involving the brain, lungs, joints, or other areas of the body are much more difficult to treat.