Dermatologic Manifestations of Sporotrichosis 

Updated: Oct 17, 2019
Author: Scott D Miller, MD; Chief Editor: Dirk M Elston, MD 

Overview

Background

Sporotrichosis is a subcutaneous or systemic infection caused by Sporothrix schenckii, a rapidly growing dimorphic fungus. The organism derives its name from R B Schenck, who first reported the infection in 1898. Sporothrix species typically exist as a saprophytic mold on vegetative matter in humid climates worldwide. A dimorphic fungus, the organism exhibits mycelial forms at 25°C and a yeast form at 37°C.[1, 2, 3, 4, 5]

Cutaneous infection often results from a puncture wound involving infected cats, thorns or other plant matter. Other more unusual reported causes include insect stings, squirrel bites, and trauma induced by liposuction.[6, 7] Any compromise of the skin barrier with subsequent seeding could potentially cause infection. Sporotrichosis usually occurs sporadically as isolated cases. Occasionally, groups of individuals are infected after being exposed to the organism.[8, 9, 10]

Since approximately the beginning of the 21st century, an outbreak of increasing numbers of cases has been occurring in Rio de Janeiro, Brazil. From 1998-2004, 759 culture-proven cases have been identified and treated, predominantly among women at a median age of 39 years and predominantly among those with domiciliary or professional contact with infected cats.[8]

An outbreak in the United States in 1988 affected 84 people who handled sphagnum moss.[10] An unusually large outbreak occurred in Africa in the 1940s in more than 3000 miners who had frequent physical contact with wood timber supports. This contributed significantly to the current understanding of Sporothrix schenckii, its growth patterns, and its mechanisms of dissemination.[2, 3]

Pathophysiology

Sporotrichosis infections can be either cutaneous or extracutaneous. Cutaneous infections are most common and are subclassified into fixed cutaneous and lymphocutaneous. A few authors refer to a rarely included third subclass of cutaneous sporotrichosis in which diffuse cutaneous involvement occurs.

Fixed cutaneous infections occur at the site of inoculation and remain confined entirely to the skin. Lymphocutaneous disease results from lymphangitic spread of an infection. Satellite lesions develop along the path of the lymphatic vessels (sporotrichoid spread) and associated lymphadenopathy occurs. Extracutaneous, or disseminated sporotrichosis, can present as pyelonephritis, orchitis, mastitis, synovitis, meningitis, or osseous infection.[1, 2, 3, 11, 12]

Sporotrichosis can cause a monoarthritis, typically involving the knee.[13, 14] Many affected individuals are immunosuppressed by alcoholism or HIV infection.[15, 16, 17] Pulmonary involvement is rare.[2, 3]

Under study is the mechanism of pathogen-host interaction, including a 70-kd (Gp70) glycoprotein from the cell wall of S schenckii, which is involved in fungal adherence to the dermal extracellular matrix.[18] This protein shows promise as a possible target for passive immunity therapies.[19]

Etiology

Sporotrichosis is caused by S schenckii, a dimorphic fungus.[1]

Epidemiology

Frequency

United States

The incidence of sporotrichosis is unknown. As an unreported, sporadic disease, its incidence is difficult to estimate. The mold itself is endemic to the Missouri and the Mississippi River Valleys.[2, 3]

International

Sporotrichosis is the most common subcutaneous mycosis in South America.[20, 21] Most reported cases occur in Mexico, followed by the remaining Americas, Australia, Asia, and Africa. Sporotrichosis is rare in Europe.[2, 3] However, it has been described as endemic in northeast China.[22, 23]

Sex

In the past, males were affected more often than females due to occupational-related risks for puncture wounds. With the 1998 outbreak in Rio de Janeiro, Brazil, women with exposure to infected cats currently account for the predominant number of new cases.[2, 3]

Age

Sporotrichosis may occur in any age, but it typically affects adults, reflecting their more frequent participation in veterinary care, gardening, woodworking, and occupational situations in which puncture wounds may occur.[2, 3, 8, 9, 10]

Prognosis

Localized disease responds well to treatment. The morbidity of cutaneous infections is generally low, although therapy can be prolonged and can have potentially serious adverse effects. Scarring can result at ulcerated sites.[1] Systemic infections can be life threatening, especially in the immunocompromised host.[2, 15, 16, 17]  Systemic disease requires prolonged treatment with potentially toxic systemic therapy.

 

Patient Education

For patient education resources, visit the Infections Center. Additionally, see the patient education article Sporotrichosis.

 

Presentation

History

Most patients relate a history of a recent prick injury at the site of infection. Clinical disease usually becomes apparent within 3 weeks of injury; however, the interval from injury to apparent infection may be as long as 6 months. The injuries are attributed to a variety of causes, including rose thorns, hay, sphagnum moss, conifer needles, mine timbers, and infected cats. The characteristic skin lesion is a dermal or subcutaneous nodule that may ulcerate. As the infection spreads along the regional lymphatic chain, satellite nodules develop along with associated regional lymphadenopathy. The infection may disseminate to cause systemic disease.[1, 2, 3]

Physical Examination

Lymphocutaneous sporotrichosis is the most common presentation. Symptoms usually arise within 3 weeks of injury. A subcutaneous nodule develops at the site of inoculation and may ulcerate as the result of central abscess formation. Satellite lesions form along the associated lymphatic chain and lymphadenopathy subsequently develops.[1, 2, 3, 8, 9]

See the image below.

Close-up of an ulcerated nodule reveals the satell Close-up of an ulcerated nodule reveals the satellite lesions characteristic of lymphangitic (sporotrichoid) spread.

Fixed cutaneous disease also is known as nonlymphatic sporotrichosis. This appears as a scaly, acneform, verrucous or ulcerative nodule that remains localized. Satellite lesions and lymphadenopathy do not occur in this form of sporotrichosis. Fixed cutaneous lesions may rarely resemble pyoderma, rosacea, pyoderma gangrenosum, and keratoacanthomas.[1, 2, 3, 8, 9, 24]

Disseminated disease can result in pyelonephritis, orchitis, mastitis, arthritis, synovitis, meningitis, osseous infection, or, rarely, pulmonary disease. Cutaneous lesions can occur in the setting of disseminated infection.[1, 2, 3, 8, 9]

Clinical signs and symptoms may be blunted in the presence of elevated glucocorticoid states or systemic steroid therapy. Sporotrichosis in this setting has resembled erysipeloid cellulitis.[15]

 

DDx

 

Workup

Laboratory Studies

Fungal cultures

S schenckii readily grows on Sabouraud dextrose agar at 25 º C as a lobated, smooth or verrucous, moist, cream-colored colony with occasional aerial mycelium, maturing to a black leathery colony. Yeast growth at 37 º C must be demonstrated to confirm Sporothrix. Inform the laboratory that sporotrichosis is clinically suspected. The organisms are characteristically scarce in tissue and may not be detected with tissue stains alone; therefore, cultures are essential.

Mycobacterial cultures

Perform cultures to rule out mycobacterial infection. The laboratory should be alerted to the possibility of an atypical mycobacterial infection, particularly if Mycobacterium marinum is suspected, to ensure that appropriate cultures are performed.

Tissue Gram stain

Gram stain is performed to rule out other infective or foreign body processes.

Acid-fast stain

Staining of tissue or purulent discharge may assist in the evaluation of possible mycobacterial infection. The paucity of organisms in such infections necessitates the use of cultures if infection is clinically suspected; a negative acid-fast bacillus (AFB) stain does not adequately rule out infection.

Imaging Studies

Perform chest radiography if pulmonary symptoms are present.

Other Tests

Intradermal skin testing using sporotrichin as an antigen to diagnose sporotrichosis is not routinely used because of its high false-positive and false-negative rates.

Urine, semen, and cerebral spinal fluid cultures, as well as fine-needle aspirate or tissue biopsy cultures are indicated based on suspicion of systemic disease.

Procedures

Obtain appropriate tissue for hematoxylin and eosin, tissue cultures, Gram stain, Fite stain, and fungal stains.

Histologic Findings

A nonspecific granulomatous reaction with pseudoepitheliomatous hyperplasia is typically present. Rarely, periodic acid-Schiff staining reveals the round to oval, cigar-shaped spores within the granuloma. The rare extracellular asteroid bodies of eosinophilic spicules surrounding a central yeast are specific for sporotrichosis, as asteroid bodies seen in other granulomatous reactions are intracellular, filamentous myelin figures that contain lipid.[2, 25]

 

Treatment

Medical Care

Systemic antifungal agents are the mainstay of treatment. Antifungal agents are used for fungicidal or fungistatic eradication of the infective organism S schenkii.[26, 27]  An increase in cutaneous induration, redness, and local lymphadenopathy may be expected after treatment is started, resulting from an increased immune response to the antigenic challenge of the killed fungus. Thermal adjuvant therapy to systemic antifungals may be beneficial, as S schenckii does not survive above 39°C.[26, 27] Passive immunization with monoclonal antibody against a 70-kd putative adhesin of S schenckii induces protection in murine sporotrichosis, giving promise for future therapies for this and similar deep-space fungal infections.[19]

Surgical Care

Surgery combined with antifungals for localized pulmonary disease has proven beneficial.[27]

Consultations

Consultations may include an infectious disease specialist and/or an internist and subspecialists as indicated by organ system involvement.

 

Guidelines

Clinical Practice Guidelines

Clinical practice guidelines for the management of sporotrichosis have been issued by the Infectious Disease Society of America (IDSA).[27]

Per the IDSA Website, these guidelines are current as of October 2014.[28]

Lymphocutaneous/cutaneous sporotrichosis

Administer itraconazole at 200 mg/d.

In patients who do not respond, administer itraconazole at 200 mg twice daily, 500 mg twice daily, or add potassium iodide (see below).

In patients intolerant of itraconazole, administer fluconazole at 400-800 mg/d or local hyperthermia.

Osteoarticular sporotrichosis

Administer amphotericin B and switch to itraconazole after therapeutic response.

Administer amphotericin B lipid formulation at 3-5 mg/kg/d.

Administer amphotericin B deoxycholate at 0.7-1.0 mg/kg/d.

Administer itraconazole at 200 mg twice daily for at least 12 months.

Confirm serum therapeutic levels after 2 weeks.

Pulmonary sporotrichosis

Antifungals are administered for localized disease after surgery, and this is also for initial therapy for severe infections.

Administer amphotericin B and switch to itraconazole after therapeutic response.

Administer amphotericin B lipid formulation at 3-5 mg/kg/d.

Administer amphotericin B deoxycholate at 0.7-1.0 mg/kg/d.

Administer itraconazole at 200 mg twice daily for at least 12 months.

Confirm serum therapeutic levels after 2 weeks.

Meningeal and disseminated (systemic) sporotrichosis

Administer amphotericin B and switch to itraconazole after therapeutic response.

Administer amphotericin B lipid formulation at 3-5 mg/kg/d.

Administer amphotericin B deoxycholate at 0.7-1.0 mg/kg/d.

Administer itraconazole at 200 mg twice daily for at least 12 months.

Confirm serum therapeutic levels after 2 weeks.

Pregnancy

Administer amphotericin B lipid formulation at 3-5 mg/kg/d.

Administer amphotericin B deoxycholate at 0.7-1.0 mg/kg/d.

Avoid azoles.

Pediatric cutaneous sporotrichosis

Administer potassium iodide, 1 drop 3 times daily, increasing as tolerated to a maximum of 1 drop/kg or 40-50 drops 3 times daily, which ever is lowest.

Pediatric disseminated sporotrichosis

Administer amphotericin B deoxycholate at 0.7 mg/kg/d, followed by itraconazole at 6-10 mg/kg, not to exceed 400 mg/d.

 

Medication

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and prevent complications. Continue systemic therapy until clinical resolution is achieved, typically 4-6 months.

Antifungal agents

Class Summary

These agents are used for fungicidal or fungistatic eradication of the infective organism S schenkii.

Amphotericin B (AmBisome)

Amphotericin B is produced by a strain of Streptomyces nodosus; it can be fungistatic or fungicidal. Amphotericin B binds to sterols, such as ergosterol, in the fungal cell membrane, causing intracellular components to leak with subsequent fungal cell death. This is the drug of choice for systemic disease, although more recent literature indicates itraconazole or terbinafine may replace amphotericin B as the drug of choice for systemic sporotrichosis.

Itraconazole (Sporanox)

Itraconazole is a synthetic triazole antifungal agent that slows fungal cell growth by inhibiting cytochrome P-450-dependent synthesis of ergosterol, a vital component of fungal cell membranes. Itraconazole is the drug of choice for cutaneous disease and second drug of choice (likely to soon be first DOC) for systemic disease. It is available as a 100-mg capsule.

Potassium iodide (SSKI, Pima)

Potassium iodide is a saturated solution containing approximately 142 g potassium iodide in 100 mL water. It inhibits thyroid hormone secretion. The mechanism of action against Sporothrix is unknown. It is the third drug of choice for cutaneous disease. Potassium iodide is not effective for systemic disease. It contains 8 mg of iodide per drop and may be mixed with juice or water for intake.

Fluconazole (Diflucan)

Fluconazole is a synthetic oral antifungal (broad-spectrum bistriazole) that selectively inhibits fungal cytochrome P-450 and sterol C-14 alpha-demethylation. It is the fourth drug of choice for systemic disease, modestly effective and thus reserved for itraconazole-intolerant patients.

Terbinafine (Lamisil)

Terbinafine is a synthetic allylamine hypothesized to act by inhibiting squalene epoxidase, thus blocking synthesis of ergosterol, a vital component of fungal cell membranes. Terbinafine is an alternative for cutaneous disease, with promise for systemic disease.