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Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Sporotrichosis

Sporotrichosis is a fungal infection of the skin caused by the fungus Sporothrix schenckii, which is found on decaying vegetation, rosebushes, twigs, hay, sphagnum moss and mulch-rich soil.

How does sporotrichosis arise?

The most common route of infection with S schenckii is via the skin through small cuts, scratches or punctures from thorns, barbs, pine needles or wires. Sporotrichosis does not appear to be transmitted from person to person but there are reported cases of transmission from infected cats to humans. In very rare cases, spore-laden dust can be inhaled or ingested and in people with a weakened immune system cause disseminated (widespread) sporotrichosis.

People at risk of contracting sporotrichosis include farmers, nursery workers, landscapers and gardeners. Adult males are, by their occupation, most exposed to the risk of infection.

What are the clinical features of sporotrichosis

Depending on the severity of infection and the overall well-being of the individual, sporotrichosis can present in several ways. Skin disease is the most common.

Presentation Features
Skin disease
  • Patients are typically well without fever
  • Lesion develops at the site of a scratch
  • Nodules appear under the skin along the lymphatic channels
Lung disease
  • Patients usually have severe underlying chronic lung disease and present with pneumonia
  • They may or may not have skin lesions
Bones & joint disease
  • Patients typically present with a subacute or chronic inflammatory arthritis involving one or more joints
  • They may or may not have skin lesions
Disseminated disease
  • Patients present with skin lesions but may have other organ involvement including the eye, prostate, oral mucosa, larynx and brain
  • Spreading usually occurs only in people with a weakened immune system, e.g. HIV or AIDS patient

Cutaneous and lymphocutaneous sporotrichosis

The lymphocutaneous route is the most common presentation of sporotrichosis and is sometimes described as sporotrichoid spread. It occurs following the implantation of spores in a wound. Lesions usually appear on exposed skin and often the hand or forearm is affected, as these areas are a common site of injury. Features of cutaneous sporotrichosis include:

Diagnosis of sporotrichosis

Microscopy and culture of infected tissue is performed to identify the presence of Sporothrix schencki. Other lymphocutaneous infections can mimic the lesions of sporotrichosis so it is important to perform tests to confirm diagnosis.

Skin biopsy can be helpful. Histopathology reveals a granulomatous infection with abscess formation. The organisms may be identified using special stains.

Treatment of sporotrichosis

Treatment of sporotrichosis depends on the site infected.

Site of infection Treatment
Skin
Bones and joints
  • Difficult to treat and rarely respond to potassium iodide.
  • Itraconazole orally for months or even up to a year.
  • Amphotericin IV if oral therapy ineffective.
  • Surgery to remove infected bone.
Lungs
  • Potassium iodide, itraconazole and amphotericin used with varying degrees of success.
  • Infected areas of lung may need to be surgically removed.
Disseminated (e.g. brain infection)
  • Itraconazole may be tried
  • Amphotericin plus 5-fluorocytosine is generally recommended.
Treatment of sporotrichosis

Treatment of sporotrichosis can be prolonged but should continue until all lesions have resolved. This may take months or years, and scars may remain at the original site of infection. However, most people can expect a full recovery. Systemic or disseminated sporotrichosis is usually more difficult to treat and in some cases life-threatening for people with weakened immune systems.

Patients should be advised of measures to take to prevent sporotrichosis. These include wearing gloves, boots and clothing that covers the arms and legs when handling rose bushes, hay bales, pine seedlings or other materials that may scratch or break the skin surface. It is also advisable to avoid skin contact with sphagnum moss.

Related information

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Author: Vanessa Ngan, staff writer

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If you have any concerns with your skin or its treatment, see a dermatologist for advice.