eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Sporotrichosis

Author: William P Baugh, MD, Assistant Clinical Professor of Dermatology, University of California Irvine School of Medicine and Western School of Medicine; Medical Director, Full Spectrum Dermatology; Consulting Staff, Department of Dermatology, St Jude Medical Center
Coauthor(s): Cynthia L Chen, BA, Clinical Assistant, Full Spectrum Dermatology; Brad S Graham, MD, Consulting Staff, Dermatology Associates of Tyler, East Texas Medical Center; Trinity Mother Francis Hospital
Contributor Information and Disclosures

Updated: Nov 15, 2007

Introduction

Background

Sporotrichosis is caused by the acquisition of Sporothrix schenckii, a dimorphic, saprophytic, and geophilic fungus. Although this fungal infection has been reported in temperate and tropical climates around the world, the fungus is less common in semiarid environments. S schenckii usually grows amidst decaying vegetable matter and in the soil as a saprophyte.

Because sporotrichosis may be difficult to initially diagnose, a differential diagnosis should always be generated during the clinical evaluation (see Differentials).

The association between sporotrichosis and acquired immunodeficiency syndrome (AIDS) was first reported in 1985. Although it is not considered an AIDS marker, it is included in a list of AIDS-related conditions. In immunocompromised patients, especially those with an impaired cell-mediated immunity, it can become an opportunistic infection with a possible life-threatening course.

Pathophysiology

The fungus is most commonly acquired by traumatic implantation into the skin, causing a local pustule or ulcer with nodules developing proximally along the draining lymphatics. Once implanted, this saprophytic fungus can grow in human tissues. When recognized by the immune system, an inflammatory response occurs. Physical signs and symptoms relate to the location and degree of inflammation that ensues. Primary organ systems involved in sporotrichosis include the skin and the lungs, although infections at other sites have been reported. Little systemic illness usually occurs, unless the fungus is inhaled or acquired by a patient who is immunocompromised. Inhalation may cause a granulomatous pneumonitis. In a host who is immunocompromised, disseminated infection can occur from skin involvement or from primary pulmonary infection. For instance, one case has been reported of laryngeal and respiratory tract sporotrichosis after steroid inhaler use.¹

Clinically, sporotrichosis may manifest as either an acute or a chronic subcutaneous mycotic infection. Although the acute phase is most common, chronic nodular lymphangiitis also reportedly develops in some cases. A minor puncture wound or splinter is sufficient to inoculate the fungus into the tissue.

Frequency

United States

Sporotrichosis is an uncommon fungal infection of unknown frequency.

International

Distribution is global, but incidence is unknown. Deep mycoses have mainly been reported in the tropics and subtropics. A recent endemic of lymphocutaneous sporotrichosis were reported in Peru.² In Rio de Janeiro, a series of cat-transmitted sporotrichosis epidemics have occurred.³

Mortality/Morbidity

Sporotrichosis is usually associated with minimal morbidity. Increased morbidity and, rarely, mortality may occur if the diagnosis is delayed, if the fungus infects patients who are immunologically compromised, or if inadequate or inappropriate therapy is rendered.

Race

Sporotrichosis has no racial predilection.

Sex

Sporotrichosis occurs in men, women, and children. Men have a higher risk of acquiring this fungus because they have greater environmental exposure from outdoor occupations.

Age

Sporotrichosis may occur in people of any age. Yet, in children, sporotrichosis tends to present more frequently with a solitary ulcerative nodule. This is in contrast to adults in which a classic lymphocutaneous form is more common.

Clinical

History

To evaluate a patient with possible sporotrichosis, investigate the history of risk factors for acquiring the fungus. Several predisposing factors may place a person at increased risk for developing sporotrichosis. Contact with certain plants known to harbor this fungus (eg, roses, sphagnum moss, salt-marsh hay, prairie hay) places patients at increased risk for the disease. The risk of this contact-acquired infection is increased among people in certain occupations, such as farmers or florists. Typical introduction of S schenckii into the skin has been described as occurring via a thorn or wood splinter; infections have also been reported in medical technicians who were exposed to tissue or culture specimens of S schenckii.

Certain diseases, such as diabetes mellitus and alcoholism, also predispose a patient to develop localized disorders. In certain settings, patients who are immunocompromised are at risk for developing disseminated sporotrichosis.

Physical

Overall, this fungal infection most commonly affects the dorsum of the hands or fingers. Various primary lesions have been described, ranging from an erythematous papule or pustule to an ulcerating nodule.

Sporotrichosis can be divided clinically into 2 main categories: cutaneous and systemic.

• Cutaneous sporotrichosis
  • The primary lesion is typically a pustule at the site of implantation. Erythematous papules, nodules, and verrucous plaques may also develop, along with secondary features such as ulceration and serosanguineous fluid drainage. Surprisingly, these lesions produce relatively few symptoms.
  • Lymphangitic cutaneous sporotrichosis is the most common form of the disease.
    • Lymphangitic cutaneous sporotrichosis is usually found on an exposed skin surface at the site of traumatic inoculation. A classic clinical setting would be an adult male who acquired a splinter that, despite removal, continued to produce an area of inflammation.
    • A pustule may slowly grow and may develop into a plaque or nodule. This nodule may eventually ulcerate. Examination proximally along the affected limb usually reveals small, deep-seated, satellite erythematous nodules along lymphatic drainage. If left untreated, the fungal infection continues to spread proximally, producing a significant amount of skin inflammation, abscesses, thickened lymphatic cords, lymphadenitis, and, eventually, systemic spread.
  • Spontaneous resolution may occur. Typically, early in the course of the disease, the patient's health is minimally affected, and the infection site bears minimal symptoms.
  • Cutaneous forms of sporotrichosis also include fixed cutaneous, cellulitic, and mycetomalike. Of these, fixed cutaneous sporotrichosis is the second main cutaneous form of the disease.
    • In its fixed cutaneous form, the fungus remains localized to the implantation site and no proximal lymphangitis or lymphadenopathy develops.
    • The fixed cutaneous form may tend to take on more of a verrucous plaquelike appearance. This form may represent enhanced host immune response to the fungus, possibly because of prior exposure. Skin surveys using the sporotrichin skin test have demonstrated that a positive test result occurs in up to 10% of certain populations, suggesting a history of prior exposure to S schenckii.
• Systemic sporotrichosis
  • Less common systemic forms of sporotrichosis usually follow inhalation of the fungus. A pulmonary infection ensues, which serves as the primary dissemination route. Systemic sporotrichosis can be divided into a pulmonary form and a disseminated form, both causing higher morbidity and mortality than cutaneous sporotrichosis.
  • Pulmonary infection may remain localized to the lung or may disseminate to other body sites, including the skin, joints, bones, internal organs, and meninges. For instance, one case has been reported of laryngeal and respiratory tract sporotrichosis after steroid inhaler use.
  • This clinical situation has often been found in persons with alcoholism.
  • Erythema nodosum and vascular lesions resembling polyarteritis nodosum have also been reported in patients with sporotrichosis.
• Clinical types of sporotrichosis
  • Localized cutaneous (chancriform) type: A subcutaneous papule or pustule develops at the site of inoculation after several weeks. Surrounding skin develops a pink-to-violaceous papulonodule, which may subsequently develop into a painless ulcer. The ulcer border is often ragged and undermined and draining a serosanguineous exudate. Draining lymph nodes may become tender and swollen.
  • Chronic lymphangitic (sporotrichoid) type: This is the most common and best recognized form of sporotrichosis; it may follow the chancriform type described above. Lymphangitic spread of the fungus produces nodular swellings in a linear array, spreading proximally up the affected extremity. Palpable lymphadenopathy is often an associated finding.
  • Fixed cutaneous sporotrichosis: Crusted verrucous plaques may occur in this type and are often found on the faces of children or the upper extremities of adults.
  • Disseminated sporotrichosis: The fungus spreads hematogenously to the skin, joints, eyes, and CNS. Multiple crusted and ulcerating papulonodules may occur. This form may have a widespread distribution (sparing the palms of the hands and the soles of the feet). The primary source of infection may be the lungs, or dissemination may occur from a cutaneous site in a patient who is immunocompromised.

Causes

Sporotrichosis is typically acquired by inoculation of the fungus into the skin during contact with certain plants or animals. Classic scenarios include skin puncture by a splinter or rose thorn. Bites or scratches from sick animals such as cats, dogs, birds, and armadillos represent another source of infection.

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