Sporotrichosis

definition and PathogenesisTop

1. Etiologic agent: Sporotrichosis, also known as “rose gardener’s disease,” is caused by dimorphic fungi from the Sporothrix schenckii complex. S schenckii is the most common etiologic agent worldwide, but S brasiliensis is an emerging cause of sporotrichosis in Brazil and other parts of South America. In humans, the fungus occurs in the yeast form; in soil, it produces mycelial hyphae.

2. Reservoir and transmission: The fungus enters the skin through small cuts or scrapes in contact with sphagnum moss, rose thorns, hay, other plants, and soil. Sporotrichosis can also affect animals, particularly cats in South America, which may serve as sources of infection for humans. In rare cases infection occurs via inhalation of conidia.

epidemiologyTop

S schenckii is found worldwide in soil, wood, and on plants. Infections are more common in tropical regions, as warm and moist environments favor reproduction of the pathogen. Endemic areas include Brazil, Peru, Uruguay, Mexico, Japan, and India. Occupational and leisure activities that involve handling of plant materials, such as gardening and farming, pose a high risk of infection. Armadillo hunting is a recognized risk factor in Uruguay. In Brazil, infections are more common in cat owners and veterinarians. Outbreaks due to wooden supports in gold mines, pine seedlings, and sphagnum moss have also been described. Sporotrichosis is an opportunistic infection in patients with compromised immunity (especially in those living with HIV infection/AIDS at CD4+ cell counts <200/microL), and infection tends to be much more severe in this population than in immunocompetent hosts.

clinical features and natural historyTop

The classic form of the disease, lymphocutaneous sporotrichosis, develops several weeks following percutaneous exposure (usually on a distal extremity such as the hand). The primary lesion is a nonhealing papulonodular, erythematous, and painless lesion that later ulcerates. Secondary lesions similar to the primary lesion develop proximally in a linear pattern along lymphatic channels (sporotrichoid spread): Figure 1. Lymph node involvement and systemic symptoms are rare. Fixed cutaneous (plaque) sporotrichosis is characterized by formation of a chronic, hyperkeratotic plaque that waxes and wanes over months and does not spread via lymphatic channels.

Extracutaneous infection is very rare, and diagnosis is often delayed. Osteoarticular infection is the most common extracutaneous manifestation. It most often affects a joint in an extremity and involves joint pain and swelling with minimal systemic symptoms. Infection via the respiratory route leads to primary pulmonary sporotrichosis, which is characterized by pulmonary infiltrates and cavitary lesions. Primary pulmonary sporotrichosis is most common in middle-aged men with chronic obstructive pulmonary disease (COPD) or alcohol use disorder. Disseminated (multifocal) disease is most often reported in patients living with HIV infection/AIDS or other immunosuppressing condition and can present with disseminated cutaneous lesions, visceral disease, or fungemia. Chronic meningitis is most often a result of disseminated disease but can also develop as an isolated infection in immunocompetent patients.

diagnosisTop

Biopsy material from a cutaneous lesion may contain yeasts (classically cigar shaped, but rounded and oval forms are also seen) that are visible with periodic acid–Schiff (PAS) staining; however, multiple fields of view may need to be examined as yeast are not abundant in immunocompetent patients. Yeast may be surrounded by strongly eosinophilic, amorphous material with radiating star-like configurations called asteroid bodies. Asteroid bodies are the result of the Splendore–Hoeppli phenomenon and are not specific to S schenckii. Culture is the gold standard of diagnosis from clinical specimens, but it is not very sensitive and repeated attempts at culture may be required due to low organism burden. Growth of the mold form of S schenckii is observed at room temperature, and thermal conversion to the smooth yeast form occurs at 37 degrees Celsius. Serologic assays have been described for epidemiologic purposes. The pathogen can also be detected with molecular assays, but none are available commercially.

TreatmentTop

Lymphocutaneous and cutaneous sporotrichosis: Oral itraconazole 200 mg daily is a first-line treatment method in nonpregnant patients and is continued until 2 to 4 weeks after lesions resolve (usually a total of 3-6 months).Evidence 1Strong recommendation (benefits clearly outweigh downsides; right action for all or almost all patients). Moderate Quality of Evidence (moderate confidence that we know true effects of the intervention). Quality of Evidence lowered due to imprecision and observational data and increased due to the observed response rate. Kauffman CA, Bustamante B, Chapman SW, Pappas PG; Infectious Diseases Society of America. Clinical practice guidelines for the management of sporotrichosis: 2007 update by the Infectious Diseases Society of America. Clin Infect Dis. 2007 Nov 15;45(10):1255-65. doi: 10.1086/522765. Epub 2007 Oct 8. PMID: 17968818. High-dose oral itraconazole (200 mg bid), terbinafine, saturated solution of potassium iodide, fluconazole (only if no other agent is tolerated), and local hyperthermia (in pregnant and nursing women) can also be used as alternative treatment options.

Extracutaneous sporotrichosis: Nonsevere osteoarticular or pulmonary disease can be treated with oral itraconazole 200 mg bid for 12 months. Consider surgical consultation for resection of localized pulmonary disease. For severe pulmonary infection, multifocal osteoarticular disease, meningitis, and disseminated sporotrichosis, treat with lipid amphotericin B formulation initially, followed by a step down to itraconazole for ≥12 months. Chronic suppressive therapy with itraconazole may be needed for meningitis and in patients with AIDS or other immunocompromising conditions until immunosuppression is reversed (if possible).

preventionTop

Exposure can be prevented by wearing puncture-resistant gloves, long sleeves, and protective footwear when handling plants and soil. Avoid scratches and bites from infected cats. In patients with HIV infection, antiretroviral therapy is an important means to prevent opportunistic infection. No vaccine is available for human use.

FiguresTop

Figure 10.8-1. Sporotrichosis: lesions starting on the dorsum of the distal right middle digit then spread more proximally in sporotrichoid fashion. Photograph courtesy of Dr Mohannad Abu-Hilal.