Sporothrix schenckii

• Dimorphic fungus that causes rose-handler's disease

Background

Microbiology

• Dimorphic fungus with a hyaline, hyphated mold phase at 25ºC, and a round-to-oval budding yeast phase at body temperature
• Produces melanin, a virulence factor

Epidemiology

• Found in soil, decomposing plant matter, and peat moss worldwide (but most often in moist tropical or subtropical zones)
  • Increasing frequency in Italy
• Acquired by traumatic implantation or inoculation of a preexisting wound
• Can also be acquired by cat scratches
• Hosts include humans, cats, horses, dogs, rodents, cattle swine, camels, etc.

Clinical Manifestations

Lymphocutaneous

• Common cause of nodular lymphangitis
• Incubation period 7 to 30 days
• Nodules can be 2 to 4 cm, and appear along the lymphatics, typically in the arms and legs (and face, in children)
  • They become indurated, then ulcerated
• May have regional lymphadenopathy
• Usually mild or no systemic symptoms

Fixed cutaneous

• Only a single lesion, fixed at the point of inoculation
• Lesions may be papular, plaques, nodular, verrucous, or ulcerated

Disseminated or multifocal

• Only occurs in patients with immunodeficiency, including alcoholism, diabetes, sarcoidosis, tuberculosis, transplantation, malignancy, immunosuppressive medication, or advanced HIV
  • Can be in the context of HIV IRIS
• Lesions can include ulcerations, aceniform, plaques, or crusts
• Worst prognosis is with dissemination to lungs or meninges

Extracutaneous

• Rare presentation without skin lesions, caused either by inhalation or deep inoculation
• Musculoskeletal infections are the most common, with septic arthritis followed by osteomyelitis or tenosynovitis
• Pulmonary sporotrichosis is more common in men aged 30 to 60 years, and presents similarly to pulmonary tuberculosis
  • Major risk factors: alcohol (1/3); sarcoidosis, TB, or diabetes (1/3); otherwise healthy (1/3)
• Sporotrichotic meningitis is rare and occurs in immunocompromised patients
• Can also affect eyes, genitals, or oropharyngeal mucosa

Differential Diagnosis

• See nodular lymphangitis

Diagnosis

• Sample collection
  • Deep swab or aspirate, if possible
  • Punch biopsy, can be with sterile saline if needed (not in formalin)
• Direct microscopy
  • May see yeast forms or characteristic asteroid bodies (especially from deep swabs)
• Culture
  • Sab + chloramphenicol at 25ºC for 5 to 7 days for mold form followed by BHI at 35-37ºC for 5 to 7 days for yeast form
  • Colony appearance is a white mold that becomes dark
• Molecular tests
  • Some labs have developed PCR diagnostics
• Serology
  • Tube or latex agglutination have specificity (95%) and sensitivity (98-100%)
  • Immunoassays also exist
• Sporotrichin skin test
  • Essentially like a TB skin test but for sporotrichosis
  • Only useful for epidemiologic surveys

Management

• First-line: itraconazole 100 to 200 mg po daily until 2 to 4 weeks after the lesions resolve (around 3 to 6 months)
  • Dose may be increased to 400 mg if there's a poor response, there are extracutaneous infections including osteoarticular or pulmonary disease, or the host is immunocompromised
  • Check for drug-drug interactions
• Alternatives include amphotericin B, fluconazole, and maybe terbinafine
• Can also do local hyperthermia, especially for patients who are unable to take the above medications

Special populations

• For pregnant women, use amphotericin B
• For osteoarticular infections, use itraconazole 200 mg po bid
  • Can use amphotericin B as induction
  • Duration is at least 12 months
• For severe pulmonary infection, use amphotericin B 3 to 5 mg/kg daily (liposomal), stepped down to itraconazole 200 mg po bid when better, to complete at least 12 months total
• Same treatment for disseminated disease
• For meningeal infection, use amphotericin B 5 mg/kg daily for 4 to 6 weeks, followed by itraconazole 200 mg po bid until at least 12 months
• For children, use itraconazole 6 to 10 mg/kg (max 400 mg) daily
• For severe disease in children, use amphotericin B 0.7 mg/kg daily induction then itraconazole 6 to 10 mg/kg (max 400 mg) daily

Potassium iodide

• Used more outside of developed countries, since it is cheap
• Poorly tolerated, though, with numerous side effects

Further Reading

• Pathogen Safety Data Sheets: Infectious Substances – Sporothrix schenckii.